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WORKS   OF  ELLEN   H.  RICHARDS 

PL'BLISHKU     IJY 

JOHN  WILEY  &  SONS 

43-4S    KAST    I9TH    ST.,    NEW   YORK. 

The  Cost  ofLiving  as  Modified  by  Sanitary  5cience. 

Hy  KUen  H.  Richards.  liiMruclor  in  Sanitary 
Chemistry  in  the  Massachusetts  Institute  of  Tech- 
nology, ivimi.  124  pafjes.  Cloth.  $1.00. 
Air,  Water,  and  Pood  ;  Prom  a  Sanitary  Standpoint. 
By  Lllen  H.  Richards,  with  the  assistance  of 
Alphcus  G.  Woodman,  Instruciors  in  Sanitary 
Chemistry  in  the  .Massachusetts  Institute  of  Tech- 
nology. Svo.    230  papes.     Cloth.     $2.00. 


PUBLISHED    BY 

HOME  SCIENCE  PUBLISHING  CO., 

485  TREMONT  STREET,    BOSTON,   MASS. 

The  Chemistry  of  Cooking:  and   Cleaning. 

By    Ellen     H.     Richards    and    S.     Maria    Elliott. 
Cloth.     15S  patjes.     Price  $1.00. 

Food   Materials  and  their  Adulterations. 

By  Ellen  H.  Kicliards.     Cloth.     183  pages.      Price 
$1 .00. 

Home  Sanitation. 

Revised    Edition.     Edited    by  Ellen    H.  Richards 
and  Marion  Talbot.     Paper.     85  pages.     Price  25c 

Plain  Words  about  Pood. 

Edited  by  Ellen  H.  Richards.   The  Rumford  Leaf- 
lets.    Illustrated.     Cloth.    176  pages.     Price  $1.00. 


AIR,  WATER,  AND  FOOD 


FROM   A  SANITARY  STANDPOINT. 


BY  \ 

ELLEN  H.  RICHARDS  and  ALPHEUS  G.  WOODMAN, 

Instructors  in  Sanitary  Chemistry,  Massachusetts  Institute  of  Technology. 


"'These  cannot  be  taken  as  sufficient  ...  in  the^rA.' times  when 
every  word  spoken  finds  at  once  a  ready  doubter,  i,f  not'ap  opponent. 
They  are,  however,  specimens,  and  will  serve  to,  oi'iilit  comparisons 
in  time  to  come." — Angus  Smith.  _>,    .    >,  >;  ',    > 

"The  ideal  scientific  mind,  therefore,  must  alvyafrs  toe  bei'd  in*  a 
state  of  balance  which  the  slightest  new  evidence  "rpjiy.c'.ianje  in  Ine 
direction  or  another.  It  is  in  a  constant  state  of  skecticiin:',  ki^owng 
full  well  that  nothing  is  certain."— Henry  A.  K6v:i>tjri\.  -    ■•  ,       ' 


FIRST   EDITION. 
FIRST    THOUSAND. 


NEW   YORK: 

JOHN   WILEY    &   SONS. 

London  :    CHAPMAN  &  HALL,  Limited. 

1901. 


Copyright,  1900, 

••♦  BV 

ELl,EN.'k.  RICHARDS  and  ALPHEUS  G.  WOODMAN. 


ROBERT   DRUMMOND,    PRINTER,    NEW   VORIC. 


25059 

CONTENTS. 


CHAPTER  PAGE 

I.  Three  Essentials  of  Human  Existence i 

II.  Air:  Composition,  Impurities,  Relation  to  Human  Life lo 

III.  The  Problem  of  Ventilation 19 

IV.  Methods  of   Examination 27 

V.  Water:  Source,  Properties,  Solvent  Power,  as  a  Carrier.  43 
VI.  The  Problem  of  Safe  Water  and  Interpretation  of  Analy- 
ses   • . . •  62 

VII.  Methods  of  Examination 82 

VIII.  Food   in    Relation    to    Human    Life,    Definition,   Sources, 

Classes,  Dietaries 121 

IX.  Adulteration  AND  Sophistication  of  Food  Materials 136 

X.  Methods  of  Food  Analysis 146 

Appendices,  Tables,  Reagents... i95 

Bibliography 213 


2052703 


AIR,  WATER,  AND  FOOD. 


CHAPTER  I. 

THREE   ESSENTIALS   OF   HUMAN   EXISTENCE. 

Air,  water,  and  food  are  three  essentials  for  healthful 
human  life.  Sanitary  Chemistry  deals  with  these  three  com- 
modities in  their  relation  to  the  needs  of  daily  existence: 
first,  as  to  their  normal  composition;  second,  as  to  natural 
variations  from  the  normal;  third,  as  to  artificial  variations — 
those  produced  directly  by  human  agency  with  benevolent 
intention,  or  resulting  from  carelessness  or  cupidity.  A 
large  portion  of  the  problems  of  public  health  come  under 
these  heads,  and  a  discussion  of  them  in  the  broadest  sense 
includes  a  consideration  of  engineering  questions  and  of 
municipal  finances.  This,  however,  is  beyond  the  scope  of 
the  present  work. 

The  following  pages  will  deal  chiefly  with  such  portions 
of  the  subject  of  Sanitary  Chemistry  as  come  directly  under 
individual  control,  or  which  require  the  education  of  indi- 
viduals in  order  to  make  up  the  mass  of  public  opinion 
which  shall  support  the  city  or  state  in  carrying  out  sanitary 
measures. 

A  notable  interest  in  the  subject  of  individual  health  as 


2  •  AIR,    WATKK,    AND    FOOD. 

a  means  of  securing  the  highest  individual  capacity  both  for 
work  and  for  pleasure  is  being  aroused  as  the  application  of 
the  principles  governing  the  evolutionary  progress  of  other 
forms  of  living  matter  is  seen  to  extend  to  mankind. 

Will  power  may  guide  human  forces  in  most  economi- 
cal ways,  and  may  concentrate  energy  upon  a  focal  point  so 
as  to  seem  to  accomplish  superhuman  feats,  but  it  cannot 
create  force  out  of  nothing.  There  is  a  law  of  conservation 
of  human  energy.  The  human  body,  in  order  to  carry  on 
all  its  functions  to  the  best  advantage,  especially  those  of  the 
highest  thought  for  the  longest  time,  must  be  placed  under 
the  best  conditions  and  must  be  supplied  with  ckan  air,  safe 
icafcr,  and  good  food,  and  must  be  aljle  to  appropriate  them 
to  its  use.  The  day  is  not  far  distant  wdien  a  city  will  be 
held  as  responsible  for  the  purity  of  the  air  in  its  school- 
houses,  the  cleanliness  of  the  water  in  its  reservoirs,  and  the 
reliability  of  the  food  sold  in  its  markets  as  it  now-  is  for  the 
condition  of  its  streets  and  bridges.  Nor  w'ill  the  years  be 
many  before  educational  institutions  will  be  held  as  respon- 
sible for  the  condition  of  the  bodies  as  of  the  minds  of  the 
pupils  committed  to  their  care;  when  a  chair  of  Sanitary 
Science  will  be  considered  as  important  as  a  chair  of  Greek 
or  Mathematics;  when  the  competency  of  the  food-purveyor 
will  have  as  much  weight  wnth  intelligent  patrons  as  the 
scholarly  reputation  of  any  member  of  the  Faculty.  Within 
a  still  shorter  time  will  catalogues  call  the  attention  of  the 
interested  public  to  the  ventilation  of  college  halls  and  dor- 
mitories, as  well  as  to  the  exterior  appearance  and  location. 

These  results  can  be  brought  about  only  wdnen  the  stu- 
dents themselves  appreciate  the  possibilities  of  increased 
mental  production  under  conditions  of  decreased  friction, 
such  as  can  be  found  only  when  the  requirements  of  health 
are  perfectly  fulfilled. 


THREE    ESSENTIALS    OF    HUMAN    EXISTENCE.  3 

Of  the  three  essentials,  air  may  well  be  considered  first, 
although  its  office  is  to  convert  food  already  taken  into  heat 
and  energy.  Its  exclusion  only  for  a  few  minutes  causes 
death,  and  in  quantity  used  it  far  exceeds  the  other  two. 
Again,  so  important  is  the  action  of  air  that  the  quality  of 
food  is  of  far  less  consequence  when  abundant  oxygen  is 
present,  as  in  pure  air,  than  when  it  is  present  in  lessened 
quantity,  as  in  air  vitiated  by  foreign  substances. 

Individual  habit  has  much  to  do  with  the  appreciation 
of  good  air,  and  as  our  knowledge  of  the  value  of  an  abun- 
dance of  this  substance  in  securing  great  efficiency  in  the 
human  being  increases,  we  shall  be  led  to  attach  more  im- 
portance to  the  sufficiency  of  the  supply. 

In  northern  climates  air  is  not  free  to  all  in  the  sense  of 
costing  nothing,  for  the  coming  of  fresh  air  into  the  house 
means  an  accompaniment  of  cold  which  must  be  counter- 
acted by  the  consumption  of  fuel.  A  mistaken  idea  of  econ- 
omy leads  householders,  school  boards,  and  college  trustees 
to  limit  the  size  of  the  air-ducts  as  well  as  of  the  rooms.  It 
is  therefore  necessary  to  emphasize  the  facts  which  science 
has  fully  esta'blished,  in  order  to  secure  the  survival  of  the 
fittest  of  the  race  under  the  present  pressure  of  economic 
conditions,  which  take  so  little  account  of  the  highest  wel- 
fare of  the  human  machine. 

Air.  water,  and  soil  are  the  common  possessions  of  man- 
kind. It  is  impossible  for  man  to  use  either  sellishly  without 
injury  to  his  neighbor  and  without  squandering  his  inheri- 
tance. Primitive  man  could  leave  a  given  spot  when  the 
soil  became'  offensive,  and  neighbors  were  then  too  few  to 
require  consideration:  but  neither  man  nor  beast  could  with  ' 
Impunity  foul  the  .stream  for  his  neighbor  who  had  riglits 
below  him.  The  soil  is  permanent;  one  knows  where  to  look 
for  it  and  its  pollution.     Air  Is  abundant  and  is  kept  In  con- 


4  AIR.    WATER,    AND    FOOD. 

stant  motion  by  forces  of  nature  beyond  luiman  control,  so 
that,  save  in  the  neighborhood  of  an  exceptionally  offensive 
factory,  man  does  not  often  foul  the  free  air  of  heaven;  it  is 
only  when  he  confines  it  within  unwonted  bounds  that  it 
becomes  a  menace. 

Water  is  the  next  precious  commodity  of  the  three. 
Without  it  man  dies  in  a  few  days;  without  it  the  soil  is  bar- 
ren; without  it  air  in  motion  parches  all  vegetation  and 
carries  clouds  of  dust-particles;  without  it  there  is  no  life. 
As  population  increases  it  becomes  necessary  to  collect  as 
much  of  the  rainfall  as  possible,  to  store  it  until  needed,  and 
to  use  it  with  discretion.  After  use  it  is  often  loaded  with 
impurities  and  sent  to  deal  death  and  destruction  to  those 
■who  require  it  later,  and  yet,  in  nature's  plan,  it  is  the  carrier 
of  the  world,  and  rightly  treated  and  carefully  husbanded 
there  is  enough  for  the  needs  of  all.  Its  presence  or  absence 
has  been  the  controlling  force  in  determining  the  habitations 
of  men.  In  its  office  of  carrier  it  not  only  l)rings  nourishment 
in  solution  to  the  tissues  of  the  human  body,  but  also  carries 
away  the  refuse  material.  It  is  a  cardinal  principle  in  all 
,'sanitary  reforms  to  get  rid  of  that  which  is  useless  as  soon  as 
possible.  Too  little  water  allows  accumulation  of  waste 
material  and  a  clogging  of  the  bodily  drainage  system. 

The  average  quantity  needed  daily  by  the  human  body  is 
about  three  quarts.  Of  this  a  greater  or  less  proportion  is 
taken  in  food,  so  that  at  times  only  from  a  pint  to  a  quart 
need  be  taken  in  the  form  of  water  as  such. 

Next  in  importance  to  quantity  is  the  quality,  dependent 
somewhat  upon  the  uses  to  which  it  is  to  be  put.  As  a  rule, 
the  moderately  soft  waters  are  the  best  for  any  purpose. 
For  drinking  purposes  water  must  be  free  from  dangers  to 
health  in  the  way  of  poisonous  metals,  decomposing  matters, 
^nd   disease-germs.     For    domestic    use    economy    requires 


THREE    ESSENTIALS    OF    HUMAN    EXISTENCE.  5 

that  it  should  not  decompose  too  much  soap.  Manufactur- 
ing interests  require  that  it  should  not  give  too  much  scale 
to  boilers;  for  agriculture  there  should  not  be  too  much 
alkali. 

From  the  nature  of  things,  no  one  family  or  city  can  have 
sole  control  of  a  given  body  of  water.  Those  on  the  high- 
lands may  have  the  first  use  of  the  water,  which  then  perco- 
lates to  a  lower  level  and  is  used  by  the  people  on  the  slopes 
over  and  over  before  it  reaches  the  sea  to  start  again  on 
its  cycle  of  vapor,  cloud  and  rain,  brook  and  river.  Al- 
though receiving  impurities  each  time,  there  are  many 
beneficent  influences  at  work  to  overcome  the  evils  resulting 
from  this  repeated  use.  That  which  is  dissolved  from  one 
portion  of  earth  may  be  deposited  on  another.  As  the  plant 
is  the  scavenger  of  the  air,  withdrawing  the  carbon  dioxide 
with  which  it  would  otherwise  become  loaded,  so  the  water 
has  also  its  plant  life,  purifying  it  and  withdrawing  that  which 
would  otherwise  soon  render  it  unfit  for  any  use. 

Pure  w^ater  is  found  only  in  the  chemical  laboratory;  the 
most  that  can  be  hoped  for  is  that  human  beings  may  secure 
for  themselves  water  which  is  safe  to  drink,  which  will  not 
impair  the  efficiency  of  the  human  machine. 

The  importance  of  the  third  essential  for  human  life, 
food,  and  the  close  interdependence  of  all  three,  may  be 
clearly  shown.  Of  little  use  is  it  to  provide  pure  air  and 
clean  water  if  the  substances  eaten  are  not-  capable  of  com- 
bining with  the  oxygen  of  the  air  or  of  being  dissolved  in 
the  water  or  the  digestive  juices;  of  less  use  still  is  it  to  par- 
take of  substances  which  act  as  irritants  and  poisons  on  the 
tissues  which  they  should  nourish,  and  thus  prevent  healthful 
metabolism  and  respiratory  exchange. 

And  yet  a  large  majority  of  those  who  ha\o  acquired 
some  notion  of  the  meaning  and  importance  of  pmc  air  and 


6  AIR.    WATER,    AND    FOOD. 

are  beginning  to  consider  it  worth  while  to  strive  for  clean 
water  pay  not  the  least  attention  to  tlie  sanitary  qualities  of 
food;  the  palatable  and  .-esthetic  aspects  only  appeal  to 
them. 

Steam-power  is  produced  by  the  combustion  of  coal  or 
oil.  Human  force  is  derived  by  releasing  the  stored  energy 
of  the  food  in  the  body.  The  delicately  balanced  mechanism 
of  the  human  body  suffers  even  more  from  friction  than  the 
most  sensitive  machine,  and  the  greatest  loss  of  potential 
human  energy  occurs  through  ignorance,  carelessness,  and 
reckless  disregard  of  nature's  laws  in  regard  to  food. 

It  is  necessary  to  know,  first,  what  is  the  normal  compo- 
sition of  a  given  food-material.  This  is  found  by  analyses 
of  many  typical  samples.  Second,  is  the  sample  under  con- 
sideration normal?  To  answer  this  requires  an  analysis  of  it, 
and  a  comparison  of  the  results  with  standards.  If  it  is  not 
normal,  in  what  way  does  it  depart  from  the  standard  both 
in  healthfulness  and  in  quality?  Third,  if  a  food-substance 
is  normal,  what  are  its  valuable  ingredients  and  in  what  pro- 
portions are  they  to  be  used  in  the  daily  diet? 

In  regard  to  meat,  milk,  and  fish,  the  sanitary  aspect  for 
•the  chemist  resolves  itself  into  two  questions:  Is  the  sub- 
stance so  changed  as  to  become  a  possible  source  of  poison- 
ous products?  Or  has  anything  in  the  nature  of  a  preserva- 
tive been  added  to  it?  If  so,  is  it  of  a  nature  injurious  to 
man? 

There  is,  however,  a  great  range  of  quality  in  some  of  the 
most  abundant  foodstuffs,  such  as  the  cereals,  especially  in 
the  nitrogen  content.  This  is  most  important  to  the  vege- 
tarian and  to  institutions  where  economy  must  be  practised. 
The  following  variations  in  the  composition  of  leading  cereals 
■will  illustrate: 


THREE    ESSENTIALS    OF    HUMAN    EXISTENCE  7 

Water      Nitrogenous     Crude  Carbo-  p.  .    , 

^^^^^^-      Substance.        Fat.         hydrates.        *^'°'^^-  ■^*"- 

Oats,  maximum 20.80  18.84  10-65  64.63  20.08  8.64 

"      minimum 6.21  6.00  2. 11  48.69  4.45  1.34 

"      American  hulled.  12. 11  13.57  7-63  63.37  i-30  2.03 

<:orn,  maximum 22.20  14.31  8.87  52.08  7.71  3.93 

"      minimum 4-68  5-55  i-73  72-75  0.99  0.82 

One  sample  of  wheat  flour  may  contain  14  per  cent,  of  nitro- 
genous substance,  another  may  yield  only  9.  A  clay's  ration, 
500  grams,  will  give  70  grams  of  gluten,  etc..  in  the  one 
■case  and  only  45  in  the  other.  This  difference  of  25  grams 
would  be  a  serious  factor  in  the  dietary  of  an  institution 
where  Httle  additional  proteid  is  given,  and  it  alone  might 
be  the  cause  of  dangerous  under-nutrition. 

The  next  step  would  naturally  be  to  determine  how 
deflnitely  these  varying  percentages  mean  varying  nutrition. 
To  this  end  a  study  of  vegetable  nitrogenous  products  in 
their  combination  or  contact  with  cellulose,  starch,  and  min- 
eral matter  is  needed.  Much  work  remains  to  be  done 
before  these  questions  can  be  even  approximately  answered. 

At  the  low  cost  of  one  cent  a  pound,  common  vegetables 
yield  only  about  one-fifth  as  much  nutriment  as  one  cent's 
worth  of  flour,  yet  they  contain  essential  elements  and  de- 
serve to  be  carefully  studied. 

Dried  fruits  and  nuts  are  much  undervalued  as  articles  of 
iood,  as  are  rice  and  lentils.     (See  table,  page  130.) 

The  discussion  of  food  values  will  be  found  in  Chapter 

vni. 

Probably  the  widest  field  for  the  sanitary  chemist  to-day 
is  the  study  of  the  so-called  predigested  foods,  infant  foods, 
*'  hygienic  "  preparations,  two-minute  cereals,  and  the  count- 
less proprietary  packages,  which,  designed  to  meet  the  dc- 
mancl  for  quick  results,  prove  traps  for  [hv  nnwary. 

Therefore  the  sanitary  aspect  of  food  demands  a  study 


8  AIR,  \vati:r,  and  food. 

of  normal  food  and  food  value  even  more  than  of  adulterants 
or  of  poisonous  food,  ptomaines  and  toxines.  The  cultiva- 
tion of  intelligent  public  opinion  is  most  important,  and  each 
student  should  go  out  from  a  sanitary  laboratory  a  mission- 
ary to  his  fellow  men.  That  is,  the  office  of  a  laboratory 
of  sanitary  chemistry  should  be  so  to  diffuse  knowledge  as 
to  make  it  impossible  for  educated  people  to  be  deluded  by 
the  representations  of  unprincipled  dealers.  Freedom  from 
superstition  is  just  as  important  in  this  as  in  the  domain  of 
astronomy  or  physics.  So  long  as  chemists  are  employed 
by  manufacturing  concerns  in  making  adulterated  and 
fraudulent  foodstuffs,  so  long  must  other  chemists  be  em- 
ployed in  protecting  the  people  until  the  public  in  general 
becomes  wiser.  A  part  of  the  common  knowledge  of  the 
race  should  be  the  essentials  of  healthful  living,  in  order  that 
the  full  measure  of  human  progress  may  be  enjoyed. 

There  is  needed  a  greater  respect  for  food  and  its  func- 
tions in  the  human  body,  a  better  knowledge  of  its  effect  on 
the  daily  output  of  energy,  its  absolute  relations  to  health 
and  life,  and  the  enjoyment  of  the  same.  The  familiarity 
with  these  facts  which  is  given  by  a  few  hours'  work  in  the 
laboratory  will  make  a  lasting  impression  and  will  enable  the 
student  to  benefit  his  whole  life,  even  if  he  never  uses  it  pro- 
fessionally. It  is  purely  scientific  knowledge,  just  as  much 
as  that  derived  from  a  study  of  the  phases  of  the  moon  or  the 
formulae  of  integration. 

The  variety  of  operations  in  such  work,  calling  for  great 
diversity  of  apparatus  and  methods,  is  an  educational  factor 
not  to  be  overlooked  in  laboratory  training. 

For  all  detailed  discussions  and  methods  the  reader  .s 
referred  to  such  works  as  those  of  Wiley,  Allen,  Blythe,  etc., 
but  for  the  student  who  needs  to  study,  as  a  part  of  general 
education,  only  typical  substances,  and  such  methods  as  can 


THREE    ESSENTIALS    OF    HUMAN   EXISTENCE.  9 

be  carried  out  within  the  limits  of  laboratory  exercises  in  a 
college  curriculum,  the  following  pages  are  written.  Not 
enough  is  given  to  frighten  or  discourage  the  student,  but 
enough,  it  is  hoped,  to  arouse  an  interest  which  will  impel 
him  at  every  subsequent  opportunity  to  seek  for  more  and 
wider  knowledge. 


CHAPTER  II. 

air:     composition;     impurities;     relation    to    human 

LIFE. 

The  average  adult  human  being  makes  about  eighteen 
invokintary  respirations  per  minute.  The  tidal  volume  of 
air  is  from  300  to  500  cubic  centimeters  (30  cu.  in.),  aboui 
2800  cubic  centimeters  (170  cu.  in.)  remaining  in  the  lungs 
unless  voluntarily  expelled  by  deep  breathing.  The  total 
volume  expelled  is  often  called  the  vital  capacity,  and  is  about 
3400  cubic  centimeters  for  men  and  2500  for  women.  Even 
when  at  rest  a  volume  of  7000  to  12,000  liters  (250  to  420 
cu.  ft.)  of  air  passes  through  the  lungs  of  each  individual  in 
twenty-four  hours.  Under  conditions  of  exercise  more  or 
less  prolonged  or  violent  this  volume  may  be  doubled.  The 
composition  of  the  normal  inspired  air  by  volume  is  approxi- 
mately: nitrogen  and  argon  79  per  cent.,  oxygen  20.9  per 
cent.,  other  constituents  o.i  per  cent.  The  air  as  it  leaves 
the  lungs  contains  nitrogen  79.5  per  cent.,  oxygen  16.0  per 
cent.,  carbon  dioxide  4.4  per  cent.,  and  is  saturated  with 
water-vapor.  There  has  therefore  taken  place  an  inter- 
change of  gases  (called  the  respiratory  exchange),  by  which 
oxygen  has  passed  into  the  fluids  of  the  body,  and  carbon 
dioxide  into  the  air  contained  within  the  lung-cells.  Only 
about  one-fifth  of  the  total  oxygen  is  abstracted  during  each 
tide. 

If  the  composition  of  the  inspired  air  varies  from  the 


air:     relation    to    human    life.  II 

normal,  this  exchange  is  disturbed,  owing  to  the  difference 
in  gaseous  pressure  and  in  rate  of  absorption  which  this 
variation  causes.  So  dehcate  is  the  balance  of  the  active 
forces  that  serious  disturbance  of  the  functions  of  the  livins: 
organism  occurs  if  the  percentage  of  oxygen  is  lessened  by 
one  or  two  tenths,  or  if  the  pressure  is  raised  or  lowered  by 
a  fraction  of  an  atmosphere.  It  is  true  that,  like  a  tree 
bending  before  the  wind,  the  organism  soon  adapts  itself  to 
changed  circumstances,  provided  the  change  is  not  too  great 
nor  too  suddenly  made;  but,  like  the  exposed  tree,  the  living 
being  is  never  quite  so  vigorous  and  symmetrical  as  it  would 
have  been  without  the  effort  to  overcome  disadvantageous 
conditions. 

That  a  permanent  or  habitual  lowering  of  the  oxygen  in 
inspired  air  must  be  harmful  will  be  readily  seen  from  a  con- 
sideration of  the  offtce  of  this  gas  in  the  body.  To  Lavoisier 
and  Laplace  we  owe  the  knowledge  that  animal  heat  is  de- 
rived from  a  process  of  combustion.  Lavoisier  held,  how- 
ever, that  the  seat  of  this  combustion  was  in  the  lungs,  and 
it  is  to  Pfiiiger  and  his  pupils  that  we  are  indebted  for  the 
proofs  that  it  is  in  the  tissues  themselves,  while  the  lungs 
serve  as  a  clearing-house  or  centre  of  exchange. 

By  the  union  of  the  oxygen  with  the  substances  found  in 
the  tissues  and  brought  to  them  by  the  circulating  fluids  of 
the  body  from  the  digested  food,  the  heat  necessary  for  the 
life  and  work  of  the  body  is  produced.  This  heat  is  needed 
to  keep  the  tissues  at  the  temperature  at  which  they  can  best 
accomplish  their  work,  to  give  mechanical  power  for  the  in- 
voluntary action  of  heart  and  lungs,  for  the  processes  of 
assimilation,  and  to  furnish  the  energy  for  all  voluntary  work 
and  thought.  Thus  both  water  and  food  arc  intimnlely  con- 
cerned In  the  processes  in  which  air  is  an  essential  factor. 
The  statement   made  in   the  first  sentence  of  Chapter  I  is 


12  AIR,    WATER,    AND    FOOD. 

therefore  justified,  namely,  that  air,  water,  and  food  together 
are  three  essentials  of  human  existence.  A  certain  relation 
between  tlie  three  means  health,  and  any  disturbance  of  this 
relation  means  unhealth,  by  which  term  may  be  designated 
a  condition  of  less  than  perfect  health  not  yet  so  serious  as 
to  be  called  sickness. 

Air  being  a  mere  mixture  of  the  gases  nitrogen  and  oxy- 
gen, in  no  definite  atomic  proportions,  and  carrying  varying 
amounts  of  other  substances,  gaseous  and  suspended  parti- 
cles, no  definite  composition  can  be  given.  The  dift'erence 
between  the  air  over  sea  or  forest  plateau  and  that  of  city 
streets  or  of  crowded  tenements  seems  only  slight  if  expressed 
in  per  cent.  From  20.98  per  cent,  of  oxygen  in  the  first  to 
20.87  and  20.60  in  the  last;  from  .022  per  cent,  of  carbon 
dioxide  in  the  purest  air  to  .045  in  cities  and  .33  in  rooms,  are 
the  common  variations;  and  yet  the  effect  of  these  apparently 
smaH  differences  on  human  beings  subjected  to  them  is  very 
noticeable.  It  is  customary  to  enhance  these  differences  by 
expressing  the  results  in  parts  per  10,000. 

That  the  carbon  dioxide  is  of  itself  a  disturbing  factor  is 
indicated  by  the  observed  fact  that  air  which  has  had  the  per 
cent,  of  oxygen  reduced  by  combustion  to  a  point  at  which 
a  candle  will  no  longer  burn  may  be  made  again  a  supporter 
of  combustion  by  the  removal  of  the  carbon  dioxide. 

A  practical  application  of  this  principle  is  made  in  the 
devices  used  in  diving  and  in  entering  mines  filled  with  irre- 
spirable  gases. 

There  is  a  sensible  effort  in  breathing,  and  a  feeling  of 
discomfort  is  usually  experienced,  if  the  carbon  dioxide  ac- 
cumulates to  ten  times  the  normal  amount,  or  40  parts  per 
10.000  instead  of  4.  This  is  probably  due  to  its  solubility 
and  to  its  interference  with  the  respiratory  exchange,  since 
the  interchange  of  gases  is  influenced  by  their  "  partial  pres- 


air:    relation  to  human  life.  13 

sures."  Each  gas  forming  part  of  a  mechanical  mixture 
exerts  a  partial  pressure  proportional  to  its  percentage  of  the 
mixture.  For  example,  if  atmospheric  air,  containing  20.81 
per  cent,  of  oxygen,  is  at  760  millimeters  barometric  pres- 

20.81 
sure,  the  partial  pressure  of  the  oxygen  would  be     ^^^    X 

760=158.15  millimeters.  The  following  partial  pressures 
of  oxygen  and  carbon  dioxide  in  inspired  air  and  in  the  lung- 
cells  show  the  extent  of  variation  in  dififerent  parts  of  the 
respiratory  tract: 

Inspired  Air.  Lung-cells. 

Oxygen    158.15  mm.  122  mm. 

Carbon  dioxide 0.30  mm.  38  mm. 

Gas  will  always  tend  to  diffuse  from  the  region  of  high- 
est to  that  of  lowest  pressure.  Hence  the  reason  for  the 
great  influence  of  pressure  in  causing  the  diffusion  of  oxygen 
from  the  inspired  air  into  the  lung-cells  and  for  the  converse 
movement  of  carbon  dioxide.  That  variation  in  pressure 
has  much  to  do  with  the  discomfort  is  shown  in  the  so-called 
mountain-sickness,  experienced  at  high  altitudes  in  rarefied 
air,  and  in  the  so-called  caisson-disease,  developed  in  men 
working  in  compressed  air.  If  the  passage  from  the  caissons 
to  the  open  air  is  made  gradually,  there  is  little  trouble,  but 
a  quick  change  is  often  dangerous.  A  sort  of  mountain- 
sickness  is  experienced  by  many  on  entering  a  close  room 
from  the  outside  air.  Usually  this  passes  away  in  a  measure 
as  the  organism  accommodates  itself  to  the  new  conditions. 
Even  if  the  symptoms  are  not  severe,  there  is  a  dulness  or 
an  irritability  which  is  not  conducive  to  the  best  apprehen- 
sion of  a  difficult  subject  or  to  the  fullest  enjoyment  ni  an 
entertainment. 

This  lessening  of  mental  capacity  is  csi)ecially  tn  be  dc- 


14  AIR,    WATER,    AND    FOOD. 

plored  in  the  case  of  school-children,  who  are  at  an  age  when 
respiration  is  most  frequent  and  the  need  of  pure  air  the 
greatest,  and  also  when  economy  of  effort  is  most  demanded. 
It  has  been  said  that  from  the  study  of  the  physiological 
effects  of  close  air  it  seems  to  be  indicated  that  the  evil  is 
due  to  the  change  in  the  respiratory  quotient  and  to  the  con- 
sequent change  in  blood-pressure,  which  interferes  with  the 
circulation.  The  respiratory  quotient  is  obtained  by  divid- 
ing the  volume  of  carl^on  dioxide  given  off  by  that  of  the 
oxygen  absorbed,  and  indicates  how  much  of  the  oxygen  has 
combined  with  carbon  to  form  carbon  dioxide,  since  one  vol- 
ume of  oxygen  combines  with  carbon  to  form  one  volume  of 
carbon  dioxide.  The  rate  of  exchange  is  influenced  by 
questions  of  pressure,  exposure,  temperature,  and  water- 
vapor  or  moisture,  muscular  activity,  and  the  like. 

Water-vapor  is  the  most  variable  constituent,  due  to  the 
changing  capacity  of  air  for  moisture  at  different  tempera- 
tures and  to  the  character  of  the  earth's  surface.  Whether 
over  land  or  water,  cultivated  or  forest  region,  air  at  o°  C. 
contains  only  4.87  grams  of  water  per  cubic  meter,  while  air  at 
60°  F.  (15°  C.)  can  take  up  12.76  grams,  and  at  90°  F.  holds 
33.92  grams.  Since  the  human  body  is  constr.ntly  giving  off 
moisture  from  skin  and  lungs,  and  since  this  exhalation  is  an 
important  factor  in  the  bodily  economy,  the  presence  of  ex- 
cessive moisture  in  the  air  exercises  a  decided  effect. 

On  clear,  invigorating  days  the  moisture' in  the  air  may 
be  only  30  or  50  per  cent,  of  that  required  for  complete  satu- 
ration at  the  given  temperature,  and  although  the  ther- 
mometer reading  may  indicate  85°  F.  on  a  hot  day.  little 
discomfort  follows;  but  let  the  humidity  rise  to  90  or  95  per 
cent,  while  the  temperature  remains  the  same,  and  oppres- 
sion, restlessness,  or  languor  results.  Much  the  same  effects 
are  seen  in  the  case  of  close  rooms  and  crowded  halls.     The 


air:    relation  to  human  life.  15 

watery  vapor  given  off  (about  20  grams  per  person  per  hour) 
soon  saturates  the  air,  and  the  consequent  drowsiness  and 
headache  usually  attributed  to  carbon  dioxide  will  be  felt; 
while  if  this  moisture  is  removed,  the  same  proportion  of 
carbon  dioxide  would  hardly  inconvenience  the  occupants. 
A  relative  humidity  of  60  per  cent,  is  said  to  be  the  most 
comfortable  for  house  temperature. 

In  normal  man,  exposure  to  cold  increases  the  respiratory 
exchange;  but  if  he  represses  shivering  and  keeps  still  by 
force  of  will,  it  apparently  does  not.  Politely  sitting  still  in- 
creases the  probability  of  taking  cold.  A  high  temperature 
lessens  the  production  of  carbon  dioxide  and  therefore  saves 
food.  This  may  in  part  account  for  the  oppressiveness  felt 
by  well-fed  and  warmly  clothed  persons  in  public  places  none 
too  warm  for  those  with  a  more  restricted  diet. 

Muscular  activity  increases  respiratory  exchange  and 
causes  a  demand  for  food.  A  class  of  students  passing  across 
the  campus,  up  several  flights  of  stairs,  into  a  lecture-room 
vitiate  the  air  for  the  first  ten  minutes  at  a  rate  higher  by 
one  part  of  carbon  dioxide  per  10,000  than  half  an  hour  later. 
The  exchange  is  also  stimulated  by  a  meal.  Not  only  the 
oxidation  of  the  food  itself,  but  the  muscular  activity  of  the 
alimentary  canal  and  probably  other  accompanying  activities 
call  for  an  expenditure  of  energy  which  is  supplied  by  in- 
creased heat  production. 

Sodium  sulphate  is  said  to  increase  the  various  respira- 
tory activities,  and  some  have  held  this  fact  to  be  one  reason 
for  the  beneficial  effects  of  certain  mineral  waters. 

The  amount  of  carbon  dioxide  expired  is  estimated  by 
Pettenkofer  at  .006  to  .012  cubic  foot  per  pound  of  body 
weight,  according  to  the  degree  of  exertion.  Pubncr  con- 
siders that,  in  general,  metabolic  processes  depend  also  upon 
the  proportion  of  superficial  area  to  the  total  volume  of  the 


1 6  AIR,    WATER,    AND    FOOD. 

body,  hence  the  smaller  the  animal  the  greater  the  surface  to 
the  whole  mass.  Children  give  off  in  proportion  to  their 
body  weight  about  twice  as  much  carbon  dioxide  as  adults. 
Another  estimate  gives  the  output  of  carbon  dioxide  as 
.0027  gram  per  hour  per  square  centimeter  of  surface. 

Ammonia  is  also  a  constant  component  of  the  air  of  in- 
habited places  and  is  washed  out  by  rain  and  snow,  as  will 
be  shown  in  Chapter  VI. 

Of  the  occasional  impurities,  probably  the  most  fatal  is 
carbon  monoxide  arising  from  leaking  gas-fixtures  or  de- 
fective furnaces.  This  gas  has  250  times  the  affinity  for 
haemoglobin  and  therefore  forms  with  it  a  more  stable 
compound  than  does  oxygen,  and  hence  its  presence  causes 
a  deficiency  of  the  latter  gas  in  the  blood,  giving  symp- 
toms like  those  observed  in  mountain-climbing  or  bal- 
loon ascensions.  When  the  blood-corpuscles  become  about 
one-third  saturated  the  effect  becomes  sensible;  but  if  the 
quantity  of  gas  is  considerable,  the  symptoms  are  hardly 
noticeable  before  insensibility  occurs.  For  this  reason,  glow- 
ing charcoal  and  open  gas-jets  are  the  favorite  forms  of 
cowardly  self-destruction. 

In  the  neighborhood  of  factories,  smelting-works,  ore- 
heaps,  and  of  cities  burning  soft  coal  there  is  a  noticeable 
amount  of  sulphurous  and  sulphuric  acids,  sometimes  so  con- 
siderable as  to  destroy  vegetation. 

In  places  where  gas  is  burned,  oxides  of  nitrogen  are 
formed  in  small  quantity,  the  effect  of  which  is  known  to  be 
harmful.  Minute  quantities  of  hydrogen  sulphide  and  of  com- 
pounds of  carbon  and  hydrogen  and  of  other  gases  may  be 
present,  especially  in  houses  with  defective  plumbing  or  in  the 
neighborhood  of  barns,  cesspools,  and  filthy  back  yards. 
These  may  reach  dangerous  proportions,  but,  like  carbon 


air:    relation  to  human  life.  17 

inonoxide,  should  not  be  permitted  in  or  near  any  well-regu- 
lated household. 

Soot,  being  insoluble,  accumulates  in  the  lungs,  as  a  post- 
mortem examination  of  persons  who  have  lived  for  some  time 
in  a  smoky  city  proves;  nevertheless  no  definite  ill  effects 
have  been  as  yet  attributed  to  this  cause.  This  again  con- 
firms the  inference  that  it  is  the  gaseous  constituents,  and  the 
varying  temperature  and  pressure,  which  seriously  affect  the 
respiratory  exchange 

The  following  results,  obtained  on  the  air  of  a  large  man- 
ufacturing city,  will  be  of  interest  in  this  connection:  * 

GRAMS    PER     1,000,000    CUBIC    METERS    OF    AIR.f 
Soot.  Hi,S04.  FreeNHa.         Alb.  NH3.  HNO,.  HNOj. 

1000  to  40000    7000  to  63000'     100  to  1000     97  to  557     45  to  1063      o  to  155 

»  Partly  HjSOa. 

It  is  probable  that  much  of  the  danger  ascribed  to  sewer- 
air  arises  from  other  causes.  Since  the  atmosphere  in  sewer- 
pipes  is  always  moist,  the  only  probable  source  of  organisms 
is  the  splashing  of  the  water.  Only  about  one-half  as  many 
organisms  have  been  found  in  the  air  above  flowing  sewage 
as  in  out-door  air.  Professor  Carnelley  and  Dr.  Haldane 
found  only  one-half  as  much  carbon  dioxide  and  one-third 
as  much  organic  matter  in  such  air  as  in  that  of  the  streets 
above. 

Beyond  individual  control,  and  in  a  measure  beyond  gen- 
eral control,  there  exists  suspended  matter  in  the  air:  fine 
volcanic  dust,  pollen,  spores  of  moulds  and  algcie,  dried  bac- 
teria, diatoms,  small  seeds  of  plants,  soot  and  the  finely 
pulverized  earth  from  roads  and  cultivated  and  barren  lands. 
To  this  portion  of  the  air  we  owe  beautiful  sun«:ets  and  dis- 
agreeable fogs.     To  it   main    affections  of  the  throat  and 

*  Mabery:  /.  Am.  Chem.  Soc,  17  {iSq^)-  105. 

f  See  also  Bailey:  "  The  Air  of  Lar^c  Towns,"  Snettct,  Oct.  13,  1893. 


l8  AIR,    WATKR,    AND    FOOD. 

eyes  arc  due,  and  by  it  disease  may  be  transmitted.  Some 
kinds  of  dust  lodge  in  the  air-cells  and  by  irriialion  render 
the  indiviilual  liable  to  disease,  as  statistics  of  the  mortality 
in  dust-producing-  trades  show.  In  the  air  of  houses  this 
impurity  increases  a  thousand-fold  by  means  of  the  wear  of 
furnishings  and  the  accumulation  on  them  of  deposited  par- 
ticles, by  means  of  furnace-ashes  and  dried  debris  of  all 
kinds.  Only  recently  have  the  dangers  of  this  part  of  the 
air  we  breathe  been  distinctly  pointed  out. 

Aitken  *  estimated  that  a  cubic  inch  of  air  may  carry 
2000  dust-particles  in  the  open  country,  3,000,000  and  more 
in  cities,  and  30,000,000  in  inhabited  rooms.  Among  these 
millions  there  may  be  found  from  ten  to  several  hundred 
micro-organisms,  moulds,  and  bacteria,  and,  under  certain 
conditions,  pathogenic  germs. 

As  methods  of  culture  become  more  satisfactory  and  tests 
more  universal,  it  may  be  demonstrated  that  many  old  or 
long-inhabited  buildings  furnish  several  varieties  of  patho- 
genic germs  constantly  to  the  air. 

According  to  some  authorities,  the  most  dangerous  con- 
tamination of  the  air  is  the  "  crowd-poison,"  or  organic 
matter  given  ofif  with  the  carbon  dioxide  and  moisture  in  the 
breath.  References  will  be  found  in  the  bibliography  to  dis- 
cussions of  the  subject.  No  evidence  has  ever  been  found 
in  the  course  of  investigations  in  this  laboratory,  covering 
a  period  of  fifteen  years,  that  the  healthy  human  lung  gives  off 
any  toxic  substance. 


*  Nature,  31  {1S70),  265;  41  {1880),  394. 


CHAPTER  III. 

THE    PROBLEM    OF    VENTILATION. 

From  the  preceding  chapter  it  will  be  seen  how  impor- 
tant is  the  purity  of  the  air  to  human  well-being,  and  how 
essential  is  the  diffusion  of  the  knowledge  of  the  methods 
by  which  it  can  be  secured.  It  is  often  said  that  artificial 
ventilation  is  a  modern  necessity.  Remains  of  aqueducts 
and  sewers  have  testified  to  the  sanitary  intelligence  of  his- 
toric peoples,  but  the  ventilating  fan  does  not  seem  to  have 
been  included,  although  natural  ventilation  by  shafts  and  flues 
has  been  practised  since  man  came  out  of  cave-dwellings.  It 
is  true  that  customs  have  changed  as  to  many  items  of  daily 
life.  In  cities  more  people  live  on  an  acre  of  ground,  thus 
fouling  the  air  above  and  the  ground  beneath;  more  factories 
are  belching  smoke;  more  coal  is  burned;  houses  are  built 
with  smaller  rooms  and  less  pervious  walls;  schools  and 
lecture-halls  are  more  crowded;  people  are  better  fed,  con- 
sequently there  is  more  garbage;  streets  are  macadamized, 
allowing  finely  ground  particles  to  fill  the  air  with  every  puff 
of  wind;  gas-pipes  traverse  the  walls  of  every  house  and 
pass  under  every  street;  carpets,  draperies,  and  much  passing 
in  and  out  cause  an  accumulation  of  dust  unknown  fifty 
years  ago.  Kerosene  lamps  require  more  oxygen  than  many 
candles.  Besides,  people  are  becoming  less  hardy  and  more 
sensitive  physically,  so  that  well-ventilated  living-spaces  are 
a  modern  necessity  if  human  efificiency  is  to  be  maintained. 

19 


20  AIR,    WATER,    AND    FOOD. 

As  we  have  seen,  the  air  of  open  spaces  presents  only 
very  slight  variation  at  the  same  level  or  for  several  thousand 
feet  above  it.  The  movement  of  the  air  caused  by  the  wind 
is  usually  so  rapid,  and  the  reservoir  of  air  for  many  miles 
above  the  earth  is  so  immense  in  comparison  with  the  thin 
vitiated  layer,  that  there  are  only  to  be  considered  enclosed 
spaces  in  which  human  beings  remain  for  a  period  of  time. 

To  supply  the  7000  to  12.000  liters  (250  to  430  cubic  feet) 
of  tidal  air  per  person  in  maximum  purity,  there  must  be 
brought  to  the  person  at  rest  some  1800  cubic  feet  of  air  per 
hour.  If  he  were  in  an  air-tight  chamber  12  feet  square  and 
8  feet  high,  a  man  would  reach  the  limit  of  purity  in  38 
minutes;  but  no  ordinary  room  is  air-tight,  and  when  the 
difference  between  inside  and  outside  temperature  is  consid- 
erable, a  rapid  exchange  is  taking  place  even  with  doors  and 
windows  shut. 

To  secure  the  passage  of  this  large  volume  of  air  through 
a  small  space  without  causing  a  draft  that  will  be  objected  to 
by  the  abnormally  sensitive  victim  of  modern  luxurious 
habits  is  the  problem  of  ventilation — one  not  yet  satisfactorily 
solved. 

The  sanitary  engineer  is  expected  to  design  the  appara- 
tus and  to  aid  the  architect  in  so  placing  and  proportioning 
flues,  inlets,  and  outlets  as  to  accomplish  the  desired  results. 
Unfortunately  it  is  too  common,  especially  in  the  case  of 
school  and  college  buildings,  to  economize  in  the  first  cost 
by  dispensing  with  the  services  of  the  expert  and  to  leave  to 
the  builder  and  "  practical  "  architect  all  such  details.  In 
any  case,  it  often  becomes  necessary  to  call  in  the  chernist  to 
prove  the  need  of  reform,  or  to  show  by  the  composition  of 
the  air  whether  or  not  the  ventilating  plant  is  doing  its  work 
efficiently. 

The   sanitary   inspector,   whose  business  it  is   to   decide 


air:     the    problem    of    ventilation.  21 

upon  the  legal  questions  connected  with  tenements  and  fac- 
tories, must  often  rely  upon  chemical  examinations  of  the 
air.  The  validity  of  these  depends  not  only  upon  the  per- 
fection and  delicacy  of  apparatus  and  methods  used,  but  also 
upon  the  judgment  and  intelligence  with  which  the  samples 
are  taken. 

Many  errors  in  the  construction  of  buildings  have  been 
perpetrated  because  of  an  ignorance  of  the  physical  proper- 
ties of  air  and,  consequently,  a  mistaken  notion  of  the  be- 
havior of  a  vitiated  atmosphere.  The  lecturer  on  popular 
science  who  some  forty  years  ago  enlightened  (?)  the  com- 
munity on  the  chemistry  of  daily  life  was  accustomed  to  use, 
as  a  striking  illustration,  a  glass  jar  in  which  a  small  lighted 
candle  was  instantly  extinguished  on  pouring  into  the  jar  a 
tumblerful  of  carbon  dioxide  which  had  been  collected  for 
the  purpose.  The  inference  was  plain:  carbon  dioxide  was 
heavier  than  air,  therefore  it  falls  to  the  floor  and  must  be 
allowed  to  flow  out  as  if  it  were  a  stream  of  water.  Further 
confirmation  of  this  inference  was  found  in  the  frequently 
observed  fact  that  a  candle  lowered  into  a  well  often  went 
out  just  before  the  water  was  reached. 

Hence  for  many  years  the  habits  of  thoughtful  persons 
were  formed  on  a  belief  in  the  heaviness  of  carbon  dioxide  or 
"  bad  air,"  and  in  its  tendency  to  go  to  the  bottom  of  the 
room  and  into  any  holes  it  could  find.  This  is  only  another 
instance  of  danger  in  half  a  truth.  When  do  we  find  cold 
carbon  dioxide  generated  in  living-rooms?  And  how  warm 
must  the  gas  be  in  order  to  be  lighter  than  the  ordinary  air? 
How  quickly  does  diffusion  take  place?  Until  within  a  very 
few  years  the  almost  unanimous  belief  among  the  so-called 
educated  classes  was  that  the  bad  air  could  be  let  out  by 
opening  a  window  at  the  bottom,  and,  in  spite  of  the  lessons 
which  might  have  been  learned  1)y  any  observant  person  in 


22  AIR,    WATER,    AND    FOOD. 

hanging  pictures  or  Christmas  greens,  the  common  practice 
in  private  houses,  churches,  and  schools  is  to  open  the  win- 
dows at  the  bottom. 

All  ordinary  vitiation  of  the  air  proceeds  from  a  heated 
source.  Human  breath  and  warm  air  are  lighter  than  cold 
air  and  rise  even  with  their  burden  of  carbon  dioxide.  It  is 
only  when  they  impinge  on  a  very  much  colder  surface,  as  on 
the  window-pane  on  a  very  cold  day,  that  they  become  suffi- 
ciently chilled  to  fall  without  mixing  with  the  neighboring 
air.  The  freedom  with  which  the  gases  of  the  air  mix,  as 
well  as  the  rapidity  of  the  action,  may  be  illustrated  in  a 
variety  of  ways.  Open  a  bottle  of  any  volatile  and  pungent 
substance,  as  ammonia  or  hydrogen  sulphide,  in  one  corner 
of  a  room,  and  almost  instantly  it  may  be  perceived  in  the 
most  distant  part. 

In  natural  ventilation  we  have  only  to  avail  ourselves  of 
these  characteristic  properties  of  gases;  and  whether  we  wish 
to  get  rid  of  the  light  gases  escaping  from  furnace,  stove,  or 
gas-pipe,  or  of  the  specifically  heavier  carbon  dioxide,  or  of 
the  most  dangerous  dust,  we  must  furnish  an  outlet  at  the 
place  to  which  the  fleeing  enemy  first  arrives,  lest  it  turn  and 
rend  us  for  our  ignorance. 

It  is  usually  sufficient  to  furnish  this  opportunity,  the 
current  caused  by  this  willing  escape  drawing  in  sufficient 
fresh  air  to  take  its  place  except  in  very  crowded  rooms,  and 
even  these  might  be  so  ventilated  provided  the  whole  roof 
were  one  large  ventilating  flue.  If,  however,  the  air  is  to  be 
drawn  from  the  bottom  of  the  room,  its  unwilling  current 
must  be  pulled  by  a  superior  force,  as  by  an  open  fire  on  the 
hearth,  which  heats  the  air  above  it  so  that,  in  rushing  into 
the  free  air  above,  it  draws  after  it  all  things  movable  within 
reach.  Then,  indeed,  even  the  top  of  the  room  becomes 
quickly  cleared  and  no  corner  can  escape;   but  if  the  fire  be 


air:   the  problem  of  ventilation.  23 

long  gone  out  and  the  chimney  cold,  the  reverse  takes  place 
and  cold,  heavy  air  sinks  to  the  floor,  helping  to  confine  the 
bad  air  at  the  top  of  the  room. 

What  the  cold  chimney  cannot  accomplish  the  mechani- 
cally driven  fan  can  do,  namely,  by  a  slight  comprescion 
force  a  draught  even  up  a  cold  chimney.  In  this  case  the 
very  unwillingness  of  the  air  to  take  the  prescribed  path 
helps  in  the  result  as  water  forced  through  a  mill-wheel  de- 
velops mechanical  work.  The  warmed  fresh  air  forced  in 
near  the  top  of  the  room  loses  its  velocity  as  it  mingles  with 
that  already  present,  and  finds  its  way  along  the  line  of  least 
resistance  to  the  opening  provided  at  the  bottom  of  the 
room,  into  the  flue,  but  only  in  case  there  is  no  easier  way. 

Open  doors  or  windows  interfere  with  the  prescribed 
course,  and  blindness  to  this  fact  on  the  pare  of  the  occupants 
of  mechanically  ventilated  buildings  has  caused  unjust  com- 
plaints of  the  system.  The  necessity  of  regulating  the  con- 
sumption of  fuel  and  admission  of  fresh  air  in  accordance 
with  variations  of  temperature,  as  well  as  the  great  care  and 
trouble  this  involves,  renders  the  "  natural  "  system  of  ventila- 
tion practicable  only  in  less  crowded  dwelling-houses  where 
Intelligence  can  control  the  varying  factors.  For  schools, 
lecture-halls,  or  any  enclosed  spaces  occupied  by  numbers  of 
persons  at  one  time,  some  form  of  mechanical  ventilation 
offers  the  only  hope  of  good  air  in  cold  climates.  What 
form  that  shall  take  is  for  the  engineer  to  decide.  The  chem- 
ist's part  is  to  devise  means  of  readily  determining  whether 
the  persons  in  charge  of  the  apparatus  are  using  it  to  gain 
the  results  designed  by  the  expert. 

As  a  test  of  how  nearly  practice  approaches  the  theoreti- 
cal value,  carbon  dioxide  is  taken  as  the  indicator,  since  it  is 
present  in  a  thousand  times  larger  qnantitv  than  any  other 
impurity  and  since  it  is  easily  determined.     If  the  air  has 


24  AIR.    WATER,    AND    FOOD. 

only  the  normal  amount  of  carbon  dioxide,  it  is  but  rarely 
that  it  contains  enough  of  anything  else  to  be  harmful.  The 
presence  of  hydrogen  sulphide  or  of  coal-gas  is  betrayed  by 
the  odor.  Where  the  gas-supply  is  "  water-gas,"  contain- 
ing 30  to  40  per  cent,  of  carbon  monoxide,  there  is  greater 
danger;  but  if  legal  restrictions  are  complied  with,  the  pres- 
ence of  this  can  be  detected  in  the  same  way,  viz.,  by  the 
odor. 

Danger  may  also  arise  from  the  presence  of  so-called 
"  sewer-gas,"  which,  however,  is  not  a  single  gas,  but  a  most 
complex  and  variable  mixture  of  the  more  volatile  products 
of  decomposition.  For  the  detection  of  "  sewer-air  "  chemi- 
cal tests  are  of  little  value,  since  it  contains  no  constituent 
in  sufficient  quantity  and  with  sufficient  regularity  to 
serve  as  an  index  of  its  presence.  Ill-smelling  gases  are 
given  ofif  only  when  sewage  is  about  eighteen  hours  old, 
hence  dirty  house-pipes  are  the  chief  cause  of  foul  air.  The 
delicate  sense  of  smell  is  of  value  here.  Indeed,  an  edu- 
cated nose  is  most  essential  in  all  examinations  of  house- 
air.  "  Crowd-poison,"  if  it  exists,  keeps  company  with  the 
increase  of  the  products  of  respiration,  and  if  the  incoming 
air  is  strained  or  taken  from  a  place  free  from  dust,  the  par- 
ticles added  to  the  air  which  is  in  the  rooms  will  also  be  re- 
moved with  the  carbon  dioxide. 

From  nearly  all  points  of  view,  carbon  dioxide  is  an  indi- 
cator of  the  efficiency  of  ventilation,  especially  if  combined 
with  observations  of  temperature  and  moisture.  It  is  an  in- 
dicator also  readily  understood  and  accepted  by  the  public. 

The  principles  of  ventilation  may  be  readily  illustrated  to 
a  class  by  means  of  simple  apparatus.  Such  an  apparatus, 
using  candles  and  designed  to  illustrate  the  section  of  an 
ordinary  room,  is  shown  in  Fig.  i. 

In  testing  the  efficiency  of  ventilation  of  any  room  or 


air:    the  problem  of  ventilation. 


25 


building,  it  is  necessary  to  determine  first  the  direction  of  the 
air-currents,  for  there  can  be  no  ventilation  without  currents. 
If  the  architect  who  designed  the  building,  or  the  engineer 
who  advised  the  architect,  is  responsible,  then  the  chemist 
has  only  to  follow  directions  in  taking  the  samples;  but  fre- 
quently the  chemist,  as  well  as  the  sanitary  engineer,  is  called 


Fig.  I. — Apparatus  to  Illustrate  tTie  Principles  of  Ventilation. 

upon  to  make  tests  of  rooms  and  buildings  of  which  no  plans 
are  available. 

In  the  examination  of  such  rooms,  then,  the  position  of 
flues  or  conduits,  both  inlets  and  outlets,  which  were  intended 
to  convey  air  or  which  serve  without  such  intention,  should 
first  be  located.  Possible  avenues  of  ingress  and  egress  by 
means  of  loose  windows,  cracks  around  doors,  etc.,  are  to  be 
considered.  When  there  is  great  difference  of  temperature 
between  outer  and  inner  air,  these  allow  of  quite  rapid  change 
of  air.  Some  means  of  rendering  visible  these  currents  is  de- 
sirable, such  as  smouldering  paper,  magnesium  powder,  or 
fumes  of  ammonium  chloride. 


26  AlK,    WATER,    AND    FOOD. 

When  the  direction  and  intensity  of  these  air-currents 
have  been  determined,  the  places  from  which  the  air-samples 
are  to  be  taken  may  be  chosen.  It  will  be  evident  in  what 
l^art  of  the  room  stagnation  occurs  and  where  eddies  are 
formed,  also  where  the  air  escapes. 

In  a  room  or  building  without  artificial  ventilation  the 
air-currents  are  seen  to  be  ascending  until  they  become 
chilled,  when  they  fall.  An  empty  room  will  not  show  so 
decidedly  the  rise  of  air-currents  as  will  an  occupied  one  in 
which  the  vitiated  air,  being  much  warmer,  rises  more  rap- 
idly and  cools  less  quickly.  In  taking  the  samples  all  acci- 
dental means  of  contamination  must  be  avoided  and  the 
occupants  must  be  quiet,  for  the  moving  of  persons  causes 
disturbance  in  the  air-current.  There  is  room  for  great  in- 
genuity in  this  part  of  the  examination,  as  circumstances 
greatly  modify  the  method  of  procedure.  A  fair  sample,  or 
a  sufficient  number  of  samples  to  give  a  fair  average,  must 
be  taken. 

Having  secured  and  analyzed  the  samples  of  air,  the  de- 
cision as  to  the  efficiency  of  ventilation  must  be  rendered. 

If  the  room  examined  is  a  study-  or  recitation-room,  the 
stratum  of  air  at  the  level  of  the  students'  heads  should  not 
contain  over  8  or  9  parts  per  10,000  of  carbon  dioxide,  should 
not  show  a  temperature  of  over  70°  F.,  nor  a  humidity  of 
over  35  or  50  per  cent.,  and  these  conditions  should  be  main- 
tained for  hours  at  a  time. 

For  lecture-halls  and  spaces  occupied  for  only  one  hour 
at  a  time,  wath  ample  time  between  occupation,  it  is  admis- 
sible to  allow  9  to  II  parts.  If  fan  ventilation  is  used,  the 
outlet  should  give  the  average  degree  of  contamination.  If 
no  system  is  used,  the  air  at  the  top  of  the  room  is  first 
vitiated;  only  at  the  end  of  twenty  minutes  to  half  an  hour 
do  the  lower  layers  begin  to  show  it. 


CHAPTER   IV. 

ANALYTICAL     METHODS.       DETERMINATION     OF     CARBON 

DIOXIDE. 


General  Statements. — The  methods  of  determination  all 
rest  upon  the  property  which  the  "  caustic  alkalies,"  the 
hydroxides  of  potassium,  calcium,  and  barium,  possess  of 
uniting  with  carbon  dioxide  and  forming  stable  compounds. 

Where  it  is  necessary  to  absorb  large  quantities  of  the 
gas  in  a  slight  volume  of  solution,  potassium  or  sodium  hy- 
droxide is  used.  For  nearly 
all  of  the  "  popular  tests  "  cal- 
cium hydroxide,  lime-water, 
is  used  because  of  its  harmless 
nature  and  the  ease  with 
which  it  can  be  obtained  from 
the  corner  drug-store,  or  from 
the  quicklime  procured  fro;n 
the  mason's  barrel.  For  vol- 
umetric methods  barium  hy- 
droxide is  generally  preferred, 
because  of  the  less  solubi  ity 
of  the  barium  carbonate,  it 
being  only  about  two-thirds 
as  soluble  as  the  calcium  salt. 
The  very  avidity  with  which 
these  substances  take  up  car- 
bon dioxide  is  a  hindrance  to 
the    preparation    of   standard    solutions    in    an    atmosphere 


^ 


W> 


Fig. 


28 


AIR,    WATER,    AND    FOOD. 


n 


M 


IZlLiLj 


already  rich  in  it.  Wlien  once  prepared  the  solution  must 
be  preserved  with  especial  care,  since  contact  with  the  hands 
or  a  whiff  of  the  breath  will  reduce  its  sirength  and  vitiate 
the  results.  All  such  solutions  are  best  kept  in  bottles  well 
protected  from  the  air  by  tubes  tilled  with  soda-lime  and  de- 
livered from  a  burette,  as  in  Fig.  2. 

For  some  of  the  methods  it  will  be  found  advantageous 
to  have  the  solution  measured  for  each  test  by  means  of  an 

automatic   pipette,   as  shown   in    Fig.   3. 

This  can  be  attached  directly  to  a  liter 
bottle  containing  the  stock  solution,  and, 
if  placed  in  a  suitable  case  to  prevent  in- 
jury, may  be  easily  carried  from  one 
place  to  another.  This  is  especially  con- 
venient for  several  of  the  "  popular 
tests." 

Pettenkofer    Method. — The  method 
for  the  determination  of  carbon  dioxide 
which  has  been  found  most  satisfactory 
in  accurate  work  is  a  modification  of  the 
Pettenkofer  method.* 

Principle. — In  principle  this  consists  in  absorbing  the  car- 
bon dioxide  from  a  known  volume  of  air  in  barium  hydroxide 
solution  and  titrating  the  excess  with  standard  sulphuric  acid. 
It  is  essential  for  the  complete  absorption  of  the  carbon  dioxide 
that  the  barium  hydroxide  be  largely  in  excess  so  that  not 
more  than  one-fifth  of  it  is  neutralized;  furthermore,  the  ab- 
sorbing solution  must  be  shaken  up  with  the  air  for  a  con- 
siderable time. 

Collecting  the  Samples. — The  samples  are  collected  in  four- 
or   eight-liter  bottles,   the   volume   of  which   is   accurately 

*  Pettenkofer:  Amialen,  2,  Supp.  Band  {1862),  p.  i.      Gill:  Analyst,  17 
{i8g2),  184. 


Fig.  3. 


AIR:     ANALYTICAL    METHODS.  29 

Icnown,  the  bottles  having  been  cahbrated  by  weighing  them 
filled  with  water.  These  bottles  are  provided  with  a  rubber 
stopper  carrying  a  glass  tube  over  which  a  rubber  nipple  is 
slipped.  They  are  filled  with  the  air  to  be  tested  by  means 
of  a  pair  of  nine-inch  blacksmith's  bellows,  fitted  with  valves 
so  arranged  as  to  draw  the  air  out  of  the  bottle.  The  bel- 
lows is  connected  with  a  three-quarter-inch  brass  tube  reach- 
ing nearly  to  the  bottom  of  the  bottle;  fifteen  or  twenty 
strokes  should  be  sufficient  to  replace  the  air  in  a  four-Hter 
bottle.  At  the  time  of  collecting  the  samples  the  following 
observations  should  be  recorded:  Room,  date,  time,  n'eather, 
place  ill  room,  number  of  people  present,  number  of  gas-jets  or 
lamps  burning,  condition  of  the  doors,  windozvs,  and  transoms; 
in  short,  everything  zuJiich  zvould  tend  to  affect  the  amount  of 
carbon  dioxide  in  the  air,  or  to  cause  currents  or  eddies.  The 
bottles  should  be  distinctly  labelled  and  their  volumes  re- 
corded. If  the  temperature  at  the  point  where  the  samples 
are  collected  should  be  essentially  different  from  that  of  the 
laboratory,  the  bottles  should  be  allowed  to  stand  in  the 
laboratory  for  half  an.  hour  or  until  they  have  attained  its 
temperature. 

Directions  for  Laboratory  Work. — The  solutions  of  barium 
hydroxide  and  sulphuric  acid  which  are  used  are  approxi- 
mately of  equal  strength;  but  since  it  is  impracticable  to  pre- 
pare exact  solutions  of  barium  hydroxide  and  to  keep  them 
without  change,  the  exact  value  of  the  barium  hydroxide  so- 
lution must  be  found  by  titration  against  the  standard 
sulphuric  acid,  which  is  made  of  such  a  strength  that  i  cubic 
centimeter  is  equivalent  to  exactly  i  milligram  of  COo. 
This  standardization,  as  well  as  the  subsequent  titration,  is 
best  made  in  a  small  flask  to  lessen  the  error  from  absorption 
of  carbon  dioxide  from  the  air.  It  will  be  found  most  gen- 
erally satisfactory  to  measure  into  the  flask  about  25  c.c.  of 


30  AIR,    WATER,    AND    FOOD, 

the  barium  hydroxide,  add  a  drop  of  phenolphthalein  solu- 
tion, and  titrate  with  the  sulphuric  acid  to  the  disappearance 
of  the  pink  color,  in  all  cases  the  iirst  end-point  should  be 
taken  as  the  correct  one,  because  the  pink  color  will  some- 
times return  on  standing.  This  is  due  to  the  presence  of 
minute  quantities  of  potassium  or  sodium  hydroxide  in  the 
solution.  The  alkah  sulphates  will  react  with  any  l)arium 
carbonate  which  may  be  suspended  in  the  liquid  with  the 
formation  of  alkali  carbonates  which  give  a  pink  color  with 
phenolphthalein.  The  standardization  should  be  repeated 
until  consecutive  results  are  obtained  which  check  within  0.2 
per  cent,  of  each  other. 

Dctcnnination. — Remove  the  cap  from  the  tube  in  the  stop- 
per of  the  bottle,  insert  the  tube-tip  of  the  burette  so  that  it 
projects  into  the  bottle,  and  run  in  rapidly  50  c.c.  of  barium 
hydroxide  from  the  burette.  Replace  the  cap  and  spread  the 
solution  completely  over  the  sides  of  the  bottle  while  waiting 
three  minutes  for  the  burette  to  drain.  In  doing  this  take  care 
that  none  of  the  solution  gets  into  the  cap.  Note  carefully 
the  temperature  and  barometric  pressure.  Place  the  bottle 
on  its  side  and  roll  or  shake  it  at  frequent  intervals  for  forty- 
five  minutes,  taking  care  that  the  whole  surface  of  the  bottle 
is  moistened  with  the  solution  each  time.  At  the  end  of  this 
time  thoroughly  shake  the  bottle  to  mix  the  solution,  re- 
move the  cap,  and  pour  the  solution  into  a  stoppered  bottle  of 
hard  glass  of  40  c.c.  capacity,  taking  care  that  the  solution 
shall  come  in  contact  with  the  air  as  little  as  possible.  Under 
these  conditions  a  full,  well-stoppered  bottle  may  safely  stand 
for  days  before  titration.  For  the  titration,  measure  out  with 
a  pipette  25  c.c.  of  the  clear  liquid  into  a  75-c.c.  flask  and 
titrate  it  with  the  sulphuric  acid  as  in  the  standardization. 
The  difference  between  the  number  of  cubic  centimeters  of 
standard  acid  required  to  neutralize   the   total   barium   liy- 


air:    analytical  methods.  31 

droxide  before  and  after  absorption  gives  the  number  of 
milligrams  of  dry  carbon  dioxide  in  the  sample  tested.  The 
results  may  be  expressed  in  parts  per  10,000,  by  volume, 
under  standard  conditions  (0°  and  760  mm.),  saturated  with 
moisture  (Method  i)  or  dry  (Method  2).  Tables  for  this 
purpose  will  be  found  in  Appendix  A.* 

Example. — Data:  Standardization,  i  c.c.  Ba  (OH),  = 
1.020  c.c.  H2SO4:  volume  of  bottle  =  8490  c.c;  Ba(OH)^ 
used  =  49-9  c.c.  ;  H2SO4  used  =  21.1  c.c.  ;  temperature  and 
pressure  =  21°  and  766  mm. 

Before  absorption 

49.9  c.c.  Ba(OH)2  =  49.9  X  1.020  =  50.90  c.c.  H2SO4. 
After  absorption 

49.9  c.c.  Ba(0H)2  =  ^—^  X  21. 1   =  42.12  c.c.  H2SO4. 

.•.(8490  —  49.9)  =  8440.1  c.c.  air  contain  50,90—42.12  = 

8.78  mg.  CO2. 

Method  I. — I  c.c.  CO2  saturated  with  moisture  at  21°  and 

766  mm.  weighs  1.79624  mg.  (Table  II,  Appendix  A). 

8  7S 
.-.   8.78  mg.  =  — -^^ —  =4.887  c.c.   CO2  saturated  with 

moisture. 

Hence  in  10,000  c.c.  of  air  there  are  ~ — —   X   10,000  = 

8440. 1 

5.79  parts  CO2. 

Method  2. — In  this  method  the  volume  of  air  is  reduced 
to  standard  conditions  of  temperature  and  pressure,  under 
which  conditions  the  weight  of  a  cubic  centimeter  of  dry  CO^ 
is  a  constant  quantity. 

*  Dietrich's  Table,  the  one  in  general  use,  is  not  absolutely  correct,  the 
weight  of  a  cubic  centimeter  of  carbon  dioxide  at  o°  C.  and  760  mm.  being 
somewhat  different  from  that  given  at  present  by  the  best  authorities,  but 
it  is  sufficiently  close  for  any  but  the  most  exacting  work. 


32  AIK,    WATER,    AND    FOOD. 

Thus  v'  =  T'[i  +  o.oo366(/'— /°)].  v'  =  8440.1,  t'=2i°, 
t°  =  0°;    hence  z'  =  7837.7  c.c. 

Also,  v:v"^H":H,  or  7837.7  :;»:=  760:  (766- 18. 5). 
(18.5  =  tension  aqueous  vapor  at  21°.) 

Then  v"  =  7709  c.c.  =  volume  of  air  at  0°  and  760  mm. 

I  c.c.  CO2  at  0°  and  760  mm.  weighs  1.9643  mg. 

Q    -75  4.460 

=  4.469  c.c.  CO2.  J^^  X  10,000=  5.79  parts 


1.9643  -^-^  ^  7709 

CO.,  per  10,000. 

Two  samples  are  to  be  taken,  closely  following  the  notes, 
and  the  results  calculated  by  both  methods  before  collecting 
more  samples.  Then  some  one  room  may  be  taken  and  the 
quality  of  the  air  determined  for  the  different  hours  of  the 
day,  or  a  comparison  of  different  rooms  may  be  made,  or  a 
building  may  be  tested  as  a  whole.  All  data  and  results  ob- 
tained should  be  arranged  in  tabular  form  on  a  separate  page 
of  the  note-book. 

Notes. — This  method  of  collecting  the  air  in  a  large  bottle 
possesses  a  decided  advantage  over  the  method  of  slowly 
drawing  the  air  through  barium  hydroxide  contained  in  a  long 
tube,  in  that  a  sample  represents  the  condition  of  the  air  at 
a  given  time  and  not  its  average  condition  for  a  period  of  an 
hour  or  so. 

In  collecting  samples,  care  must  be  taken  to  avoid  cur- 
rents of  air  or  the  close  proximity  of  people.  Duplicate 
samples  can  be  obtained  only  in  empty  or  nearly  empty 
rooms.  Even  two  sides  of  the  same  room  will  probably 
show  differences,  but  two  samples  taken  carefully  side  by 
side  ought  to  agree  within  0.05  part  per  10,000. 

The  chief  source  of  error  lies  in  the  contamination  of  the 
samples  or  of  the  solutions  by  air  from  the  lungs,  the  exhaled 
breath  containing  on  an  average  from  50  to  100  times  as 
much  carbon  dioxide  as  the  air  under  examination.     It  is 


air:   analytical  methods.  53 

hardly  possible  to  exercise  too  much  caution  in  collecting 
the  samples  and  in  carrying  out  the  analytical  procedure. 

All  rubber  stoppers  which  are  used  should  first  be  boiled 
in  dilute  caustic  soda,  then  in  a  dilute  solution  of  potassium 
bichromate  and  sulphuric  acid  and  thoroughly  washed. 

Popular  Tests. — I  a  addition  to  the  standard  method  for 
determining  carbon  dioxide  just  described,  there  are  also  cer- 
tain so-called  "  popular  methods  "  which  can  often  be  used 
with  advantage.  These  methods  do  not  give  so  accurate  re- 
sults as  those  obtained  by  the  standard  method,  but  on  the 
other  hand  the  apparatus  required  is  much  simpler  and  more 
compact,  can  be  more  easily  carried  from  one  place  to  an- 
other, and  if  used  carefully  and  intelligently  will  give  fairly 
good  results.  Several  of  these  simple  tests  will  be  described 
in  detail. 

(i)  Method  of  Cohen  and  Appleyard.-^ — ^Principle. — 
This  method  is  based  upon  the  fact  that  if  a  dilute  solution 
of  lime-water,  slightly  colored  with  phenolphthalein,  is 
brought  in  contact  with  a  sample  of  air  containing  more  than 
enough  carbon  dioxide  to  combine  with  all  the  lime  present, 
the  solution  will  be  gradually  decolorized,  the  length  of  time 
required  depending  upon  the  amount  of  carbon  dioxide 
present.  That  is,  the  quantity  of  lime-water  and  the  volume 
of  air  remaining  the  same  in  each  case,  the  rate  of  decoloriza- 
tion  will  vary  inversely  with  the  amount  of  carbon  dioxide. 
The  method  is  scientific  in  principle  because  it  recognizes  the 
fact  that  the  absorption  of  carbon  dioxide  by  dilute  alkali 
solutions  is  a  ^n/;c-reaction. 

Directions. — Collect  several  samples  of  air  in  white,  glass- 
stoppered  bottles  of  one  liter  capacity,  cither  by  exhausting 
the  air  from  the  bottle  with  a  pair  of  bellows  or  by  com- 
pletely filling  the  bottle  with  water  and  then  emptying  it  at 

*  Ckem.  News,  70  (i8q4),  hi. 


3h 

7.0 

4 

5.3 

4i 

5.1 

5 

4.6 

5i 

4.4 

6i 

4.2 

7i 

3-5 

34  AIK,    WATKR,    AND    FOOD. 

the  point  where  the  sample  is  to  be  taken.  Run  in  quickly 
from  the  burette  10  c.c.  of  the  standard  lime-water  (see  Re- 
agents, p.  204),  replace  the  stopper  and  note  the  time.  Shake 
the  bottle  vigorously  with  both  hands  until  the  pink  color 
disappears.  Note  the  time  required,  and  ascertain  the  cor- 
responding amount  of  carbon  dioxide  from  the  following 
table. 

TABLE. 

Time  in  Minutes  to       rn    r^^r,^r^  Time  in  Minutes  to        CO„  oer  lo  ooo 

Decolorize  the  Solution.  ^°»  P"  '°'°°°-  Decolorize  the  Solution.    ^"»  P''  '°>°°°- 

li  16.0 

li  13-8 

4  12.8 

2  12.0 

2i  II. 5 

2j  8.6 

3i  7.7 

Modified  Cohen  Method. — If  all  the  tests  of  air  by  this 
method  are  to  be  made  in  the  laboratory,  it  will  be 
found  best  to  keep  the  standard  solution  in  a  bottle  carefully 
protected  from  the  air,  and  to  draw  it  off  from  a  burette  as 
wanted  for  each  test.  In  order  to  make  the  apparatus  more 
portable  and  convenient  for  a  number  of  tests  at  a  distance 
from  the  laboratory,  the  following  modification  of  the  method 
is  used,  and  has  been  found  to  give  excellent  results.  The 
10  c.c.  portions  of  the  standard  lime-water  are  measured  into 
thin  glass  vials  which  are  tightly  closed  with  rubber  stop- 
pers. A  number  of  these  vials  can  be  filled  at  once,  since  the 
solution  will  keep  its  strength  for  a  long  time  if  the  vials  are 
clean  and  the  stoppers  have  been  boiled  with  potash  and 
bichromate  as  previously  directed.  In  order  to  avoid  get- 
ting traces  of  acid  on  the  outside  of  the  filled  vials  through 
handling,  it  is  best  to  rinse  them  off  thoroughly  and  keep 
them  in  a  beaker  under  water  until  wanted  for  use.  The 
samples  are  collected  in  the  bottles  as  before,  the  glass  stop- 


air:    analytical  methods.  35 

per  removed  for  a  second,  and  the  vial  of  lime-water  quickly- 
dropped  in,  stopper  downward.  The  bottle  is  shaken  once 
violently  to  break  the  vial,  and  is  then  shaken  with  a  rotary- 
motion  until  the  solution  is  decolorized.  If  desired,  a  bottle 
of  half  the  size,  and  smaller  vials  holding  only  five  cubic 
centimeters  of  solution,  may  be  used. 

Note. — Much  of  the  difficulty  experienced  in  the  use  of 
these  simpler  methods  arises  from  the  lack  of  definiteness  in 
the  composition  of  "a  saturated  solution  of  lime-water"  which 
is  generally  recommended  for  use  in  making  up  the  test  solu- 
tion. The  amount  of  lime  that  water  will  take  up  varies 
considerably  with  the  way  in  which  the  solution  is  made;  for 
example,  whether  the  water  is  simply  shaken  up  with  a  cer- 
tain quantity  of  lime,  or  whether  the  solution,  once  saturated, 
is  kept  standing  over  an  excess  of  lime.  For  this  reason  it 
is  much  better  to  have  the  strength  of  the  lime  solution 
definitely  fixed  by  some  method  of  titration, 

(2)  Method  of  Dr.  G.  W.  Fitz — Principle.— In  this 
method  the  volume  of  air  that  must  be  brought  in  contact 
with  a  definite  quantity  of  lime-water,  in  order  to  neutralize 
all  of  the  lime,  is  taken  as  a  measure  of  the  amount  of  carbon 
dioxide  in  the  air.  The  quantity  of  lime-water  and  the  time 
of  reaction  remaining  constant,  the  amount  of  carbon  diox- 
ide will  vary  inversely  as  the  volume  of  air  required.  In  this 
laboratory  the  same  solution  is  used  for  this  method  that  is 
used  in  the  Cohen  method.  The  apparatus  consists  of  a 
graduated  tube  or  "  shaker,"  of  about  thirty  cubic  centimeters 
capacity,  and  a  number  of  homoeopathic  vials,  each  containing 
ten  cubic  centimeters  of  standard  "  lime-water." 

Directions. — Be  sure  that  the  inner  tube  of  the  shaker 
slides  easily  within  tlic  outer  one,  then  remove  the  inner 
tube  and  pour  into  the  large  tube  the  contents  of  one  of  the 
vials.     Introduce  the  inner  tube  and  press  it  to  the  bottom 


36  AIR,    WATKK,    AND    FOOD. 

of  the  larger,  then  withdraw  it  to  the  "  T  "  mark,  the  bottom 
of  the  inner  tube  serving-  as  the  index.  Close  the  mouth  of 
the  small  tube  with  the  linger  and  shake  the  instrument  vig- 
orously for  thirty  seconds.  The  volume  of  air  thus  brought 
in  contact  with  the  solution  is  30  cubic  centimeters,  as  there 
are  25  cubic  centimeters  of  air  above  the  solution  when  the 
inner  tube  is  forced  to  the  bottom  of  the  larger.  Then  re- 
move the  finger  closing  the  small  end,  press  the  inner  tube  to 
the  bottom  of  the  larger  and  draw  it  up  again  to  the  20-c.c. 
mark,  thus  admitting  20  cubic  centimeters  of  fresh  air. 
Shake  the  apparatus  again  for  thirty  seconds.  The  total 
volume  of  air  now  used  is  30  -|-  20  c.c.  =  50  c.c.  Repeat  the 
operation  until  the  color  of  the  solution  is  discharged.  The 
rirst  trial  made  will  probably  give  the  approximate  amount 
of  carbon  dioxide,  and  subsequent  tests  with  the  other  vials 
will  aid  in  giving  the  correct  result.  After  determining  the 
volume  of  air  which  is  required  to  decolorize  the  solution 
reference  is  made  to  the  table  given  below. 

TABLE. 

Air  in  c.c.  used.  CO,  per  lo.ooo.  Air  in  c.c.  used.        CO,  per  10,000. 

30  28  91  9    Bad 

36  22  103  8 

46  18  Very  bad  117  7 

58  14  138  6 

69  12  165  5   Good 

82  10  207  4 

Notes. — The  stoppers  and  vials  should  be  washed  and 
dried  after  use  and  kept  separate,  and  the  parts  of  the  shaker 
should  be  kept  separate. 

In  using  the  shaker  see  that  the  fingers  are  clean,  or  close 
the  mouth  of  the  shaker  with  a  rubber  stopper  instead  of  the 
finger:  also  take  care  to  avoid  loss  of  liquid  upon  the  addition 
of  fresh  air.  The  same  objection  applies  to  this  method  as 
to  the  tube  method  of  Pettenkofer,  namely,  that  the  air  taken 


air:   analytical  methods.  37 

is  an  average  sample  extending  over  some  time  and  does  not 
show  its  condition  at  any  one  time.  New  stoppers  should 
be  boiled  in  dilute  caustic  soda  and  then  in  bichromate  solu- 
tion before  being  used. 

(3)  Wolpert's  Method. — Principle. — When  air  contain- 
ing carbon  dioxide  is  passed  through  lime-water  the  solution 
o-raduallv  becomes  turbid  from  the  formation  of  calcium  car- 
bonate,  and  the  richer  the  air  is  in  carbon  dioxide  the  less 
will  be  the  volume  of  air  required  to  produce  a  definite  degree 
of  turbidity.  This  is  the  principle  on  which  this  simple 
method  is  based. 

Directions. — A  small  test-tube  provided  with  a  black  ref- 
erence-mark on  the  bottom  is  filled  to  a  definite  height  with 
"  saturated  "  lime-water.  The  air  is  collected  in  a  small  rub- 
ber bulb  and  slowly  forced  through  the  solution,  the 
operation  being  repeated  until  the  reference-mark  can  no 
longer  be  seen  through  the  turbid  solution.  The  instrument 
is  first  calibrated  by  observing  the  volume  of  air  required  to 
produce  turbidity  out  of  doors  or  in  some  room  where  the 
percentage  of  carbon  dioxide  is  known,  after  which  it  affords 
a  ready  means  for  comparative  tests  in  cases  where  the  air 
contains  20  parts  or  more.  For  testing  modern  systems  of 
ventilation,  where  the  amount  is  usually  less  than  8  parts,  it 
does  not  give  reliable  results.  The  difficulties  in  the  use  of 
this  method  are  the  same  as  those  noted  under  the  Fitz  meth- 
od, with  the  increased  error  due  to  the  solubility  of  calcium 
carbonate  in  solutions  of  carbon  dioxide. 

(4)  Wolpert's  "  Luftpriifer"  (Air-tester). — This  is  an- 
other simple  instrument  for  testing  the  purity  of  the  air. 
Its  action  is  based  upon  the  well-known  fact  that  the  alkali 
carbonates  give  a  pink  color  with  phenolphthalein.  while  the 
bicarbonates  do  not.  "Ry  means  of  a  capillary  siphon  a  one 
per  cent,  solution  of  sodium  carbonate  colored  with  phe- 


38  AIR,    WATKR,    AND    FOOD. 

nolpluhalcin  is  allowed  to  drop  at  regular  intervals  upon  a 
cord  suspended  vertically.  As  the  solution  flows  down  the 
string  it  absorbs  carbon  dioxide  from  the  air,  convertiiis;-  the 
sodium  carbonate  into  the  bicarbonate,  so  that  the  lower  part 
of  the  cord  will  be  white,  while  the  upper  part  is  pink.  The 
height  of  the  dividing  line  indicates  on  a  scale  the  amount  of 
carbon  dioxide  in  the  air.  The  chief  value  of  this  instru- 
ment lies  in  the  fact  that  it  acts  continuously,  one  filling 
being  enough  to  last  for  ten  days,  and  can  be  consulted  at 
any  time  to  learn  the  condition  of  the  air,  just  as  a  ther- 
mometer is  used  to  indicate  the  temperature.  In  practice 
the  usefulness  of  the  apparatus  has  not  been  fully  realized  on 
account  of  the  dryness  of  the  air  in  ordinary  rooms,  w-hicli. 
interferes  with  the  continuous  flow  of  liquid  down  the  cord. 

Carbon  Monoxide. — The  detection  and  estimation  of 
carbon  monoxide  in  the  very  minute  quantities  in  which  it  is 
found  in  the  air  of  ordinary  rooms  is  a  problem  of  consider- 
able difficulty. 

Defection. — Probably  the  most  convenient  test  for  detect- 
ing small  quantities  is  the  blood  test.  Dilute  a  large  drop 
of  human  blood,  freshly  drawn  by  pricking  the  finger,  to  lo 
c.c.  with  w^ater.  Divide  the  solution  into  two  equal  portions, 
and  shake  one  portion  gently  for  ten  minutes  in  a  bottle  con- 
taining about  lOO  c.c.  of  the  air  to  be  tested.  Compare  the 
tints  of  the  tw^o  portions  by  holding  them  against  a  well- 
lighted  white  surface.  The  presence  of  carbon  monoxide  is 
indicated  by  the  appearance  of  a  pink  tint  in  the  blood  which 
has  been  shaken  wnth  air.  One  part  in  10,000  can  be  de- 
tected in  this  way.*  The  delicacy  of  the  test  can  be  increased 
by  examining  the  blood,  after  shaking  with  the  air,  with 
a  spectroscope.     By  collecting  the  sample  in  an  8-liter  bottle 


*  Clowes:   "  Detection  and   Estimation  of  Inflammable  Gas  and  Vapor 
in  the  Air,"  p.  13S. 


air:    analytical  methods.  39 

and  examining  it  in  this  way  o.oi  part  in  10,000  may  be  de- 
tected. 

Determination.*  —  Principle.  —  Oxidation  of  the  carbon 
monoxide  to  carbon  dioxide  by  iodine  pentoxide,  iodine 
being  Hberated  according  to  the  following  equation: 

I,05+5CO=  I2+  5CO2. 

N 

The  iodine  is  titrated  with sodium  thiosulphate. 

1000  ^ 

Directions. — Place  25  grams  of  iodine  pentoxide.  free  from 

iodine,  in  a  small  U  tube  which  is  suspended  in  an  oil-bath 

and  connected  with  a  small  absorption-bulb  containing  0.5 

gram  of  potassium  iodide  dissolved  in  5  c.c.  of  water.     Heat 

the  oil-bath  to  150°  C,  and  pass  the  air,  previously  drawn 

through  U  tubes. — one  containing  sulphuric  acid  and  the 

other  solid  potassium  hydroxide, — through  the  apparatus  at 

the  rate  of  a  liter  in  two  hours.     Titrate  the  Hberated  iodine 

N 

bv sodium  thiosulphate  and  starch. 

•^  1000  ^ 

Notes. — The  temperature  and  barometric  pressure  should 
be  noted  and  all  volumes  reduced  to  0°  C.  and  760  mm.  pres- 
sure. 

Using  1000  c.c.  of  air,  it  is  possible  to  determine  in  this 
way  0.25  part  per  10,000,  by  volume,  of  carbon  monoxide. 

The  use  of  tubes  containing  sulphuric  acid  and  potassium 
hydroxide  is  to  free  the  air  from  unsaturated  hydrocarlions, 
hydrogen  sulphide,  sulphur  dioxide,  and  similar  reducing 
gases. 

Nitrites. — The  determination  of  the  amount  of  nitrites 
or  nitrous  acid  in  the  air  can  be  readily  made  as  follows: 
Collect  a  sample  of  the  air  in  a  calibrated  eight-liter  bottle, 
as  in  the  determination  of  carbon  dioxide.     Add  100  c.c.  of 

*  Kinnicutt  and  Sanford:  Jour.  Am.  Chem.  Soc,  22  {igoo),  14. 


40  AIR,    WATER,    AND    FOOD. 

N 
approximately  —  sodium  hydroxide  solution.     (This  shouUr 

be  free  from  nitrites  and  is  best  made  by  dissolving  metallic 
sodium  in  redistilled  water.)  Shake  the  bottle  occasionally 
and  let  it  stand  for  about  twenty-four  hours.  Take  out  50 
c.c.  of  the  solution  and  determine  the  amount  of  nitrites  as 
directed  on  page  94. 

Micro-organisms. — For  the  quantitative  determination 
of  the  number  and  distribution  of  the  micro-organisms  in  air, 
the  method  employed  by  Tucker  *  in  the  examination  of  the 
air  of  the  Boston  City  Hospital  answers  very  well.  The 
apparatus  used  consists  essentially  of  three  parts:  (i)  a 
special  glass  tube  called  the  acrohioscopc,  in  which  is  placed 
the  filtering  material;  (2)  a  stout  copper  cylinder  of  about 
sixteen  liters  capacity,  fitted  with  a  vacuum-gauge;  (3)  an 
air-pump.  The  filtering  medium  which  is  used  to  retain  the 
micro-organisms  is  a  narrow  column  of  sterilized  granulated 
sugar  about  four  inches  long. 

In  using  the  apparatus,  the  required  amount  of  air  is  first 
drawn  from  the  cylinder  by  means  of  the  air-pump.  A 
sterilized  aerobioscope  is  then  attached  to  the  cylinder  and  the 
air  is  slowly  drawn  through  it,  leaving  its  germs  in  the  sugar- 
filter.  After  the  air  has  been  drawn  through,  the  aerobioscope 
is  taken  to  the  culture-room  and  the  sugar  dissolved  in 
melted  sterilized  nutrient  gelatine.  The  gelatine  is  con- 
gealed in  an  even  film  on  the  inside  of  the  tube,  where,  after 
four  or  five  days,  the  colonies  will  develop,  and  can  be 
counted  by  the  aid  of  squares  engraved  upon  the  glass. 

This  method  possesses  several  peculiar  advantages.  The 
use  of  a  vacuous  cylinder  allows  a  known  volume  of  air  to  be 
readily  asf)irated,  and  the  rate  of  flow  through  the  filter  is 
easily  controlled.     Another  great  advantage  is  the  use  of  a 

*  Report  State  Board  of  Health,  Mass..  1889,  161. 


air:    analytical  methods.  41 

soluble  filter  (sterilized  granulated  sugar),  since  insoluble 
substances  seriously  interfere  with  the  counting.  Further- 
more, the  removal  or  transference  of  the  filter  and  its  germs 
is  avoided.  The  apparatus  is  portable,  and  the  method,  as 
compared  with  others,  is  exceedingly  rapid  of  execution. 

OrganicMatter. — In  regard  to  the  presence  of  organic 
matter  in  the  air  there  is  at  present  considerable  variance  of 
opinion.  While  some  investigators  have  obtained  results 
which  indicate  the  presence  of  such  organic  matter,  it  has 
been  found  also  that  the  amount  which  is  obtained  is  very 
much  less  when  the  dust  of  the  air  is  first  removed  by  filtra- 
tion. The  quantity  of  organic  matter  is  therefore  closely  re- 
lated to  the  amount  of  dust,  and  there  is  strong  evidence  that 
this  dust  in  the  air  is  the  source  of  the  greater  part,  if  not  all, 
of  the  organic  matter,  unless  there  are  present  persons  with 
decayed  teeth,  diseased  lungs,  etc. 

The  methods  of  determination  that  are  in  general  use 
may  be  divided  into  two  groups.  In  the  first  group  are 
those  methods  in  which  the  organic  matter  is  converted  into 
ammonia  and  determined  by  Nessler's  reagent.  In  the  sec- 
ond group  the  organic  matter  is  oxidized  by  boiling  with 
dilute  potassium  permanganate,  the  excess  being  titrated 
with  oxalic  acid.  No  one  method  gives  results  which  are 
wholly  satisfactory,  the  chief  difificulties  being  to  secure  an 
absorbing  material  which  shall  itself  be  free  from  organic 
matter,  and  to  avoid  the  introduction  of  minute  particles  of 
organic  matter  or  dust  during  the  analytical  process. 

Remsen  *  and  Bergey  f  recommend  the  use  of  freshly 
ignited  granular  pumice-stone  contained  in  a  narrow  glass 
absorption-tube.  After  aspirating  a  known  volume  of  air, 
the  pumice-stone  is  transferred  to  a  flask,  the  ammonia  dis- 

*  National  Rd.  Health  Riilletin,  I,  233;  II,  517. 

f  Mis.  Coll    of  Smithsonian  Institution,  No.  1037  {/Sg6). 


42  AIR,    WATER,    AND    I-'OOD. 

tilled  off  from  alkaline  permanganate  and  estimated  by  Ness- 
ler's  reagent.  Experience  with  the  method  in  this  labora- 
tory has  shown  that  it  is  practically  impossible  to  prepare  the 
pumice-stone  so  that  it  shall  be  absolutely  free  from  organic 
matter,  and  that  the  mere  act  of  transference  of  the  absorb- 
ing material  resulted  in  a  considerable  error.  Miss  Talbot  * 
found,  furthermore,  that  all  of  the  organic  matter  is  not  con- 
verted into  ammonia  by  a  single  distillation,  but  that  a  second 
and  third  redistillation  of  the  distillates  uniformly  gave 
higher  results.  She  found  it  preferable  to  draw  the  air 
directly  through  the  boiling  permanganate,  having  the  ap- 
paratus so  arranged  that  the  condensed  steam  was  returned 
to  the  flask.  In  this  way  the  particles  of  organic  matter  were 
returned  again  and  again  to  be  acted  upon  by  the  perman- 
ganate. 

Experience  with  all  these  methods  is  well  summed  up  by 
Professor  Remsen  when  he  says:  "It  would  be  useless  to 
have  examinations  of  air  made  by  any  but  the  most  careful 
workers.  It  would  be  time  thrown  away  to  have  such  an- 
alyses made  by  the  average  practical  chemist." 

Dust  and  Soot — The  dust  in  the  air  may  be  estimated  by 
drawing  a  measured  volume  through  tubes  packed  with  cot- 
ton and  noting  the  increase  in  weight.  Soot  may  be  deter- 
mined by  drawing  the  air  through  combustion-tubing  partly 
filled  with  ignited  asbestos,  and  then  determining  the  carbon 
by  the  ordinary  methods  of  combustion. 

*  Tech  Quart.,  I  (1887),  29. 


CHAPTER  V. 

water:  its  source,  properties,  and  relation  to  life 

AND    health. 
{From  the  Householder' s  Standpoint.) 

The  metabolism  which  produces  human  energy  is  depen- 
dent upon  the  presence  of  water  in  the  tissues.  This  water 
is  derived  in  part  from  food  which,  as  eaten,  contains  from 
30  to  95  per  cent.;  in  part  from  boiled  water,  as  in  tea  and 
coffee;  or  raw  from  well  or  city  tap.  The  total  daily  supply 
per  person  for  this  purpose  from  all  sources  is  five  or  six 
pints. 

Water  is  also  necessary  to  all  forms  of  vegetable  and 
animal  life,  even  the  lowest  types,  including  those  inimical 
to  human  health.  Man  has  always  used  water  as  his  beast  of 
burden:  to  carry  ships  to  the  ocean,  to  turn  mill-wheels,  to 
generate  electrical  power.  He  has  also  forced  it  to  be  his 
scavenger,  carrying  the  refuse  of  his  activities  out  of  his  sight. 
Unless  compelled  by  legal  restrictions,  he  has  given  little 
thought  to  the  effect  on  his  neighbor  of  this  treatment  of 
their  common  property. 

In  common  law,  water  is  held  to  be  a  gift  of  nature  to 
man  for  use  by  all,  and  therefore  not  to  be  diverted  from  its 
natural  channels  for  the  pleasure  or  profit  of  any  one  to  the 
exclusion  of  the  rest.  Neither  has  one  the  right  to  return 
to  the  channel  water  unfit  for  the  use  of  his  neighbor  farther 
down  the  stream.     That  is,  there  is  no  private  ownershi])  in 

43 


44  AlK,    WATER,    AND    l-'OUL). 

surface-waters  flowing  in  natural  channels.  But  this  inter- 
pretation of  eminent  jurists  has  not  always  been  strictly  fol- 
lowed. Many  cases  have  been  decided,  especially  since  the 
rapid  growth- of  large  cities,  in  direct  contradiction  to  this 
law.  As  population  increases,  cities  need  to  go  farther  and 
farther  into  the  country  for  their  water-supply,  and  they 
often  take  from  the  few  settlers  found  there  the  right  to  the 
water  which  passes  their  doors,  for  the  benefit  of  far-away 
thousands. 

The  law  in  regard  to  that  portion  which  never  enters,  or 
which  escapes  from  visible  channels,  is  less  clear.  It  is  usu- 
ally held  that  this  water  goes  with  the  soil,  and  that  rights 
to  it  may  be  bought  and  sold:  that  wells  may  be  driven  and 
drains  dug,  even  if  a  neighbor's  supply  is  cut  ofif;  but  it  is 
always  maintained  that  no  man  has  a  right  to  place  any  sub- 
stances on  or  in  the  ground  which  shall  render  his  neighbor's 
well  unfit  for  use.  ^ 

The  changes  in  conditions  of  life  have  rendered  impera- 
tive a  careful  study  of  the  ways  and  means  of  practically  com- 
plying with  the  lawn's  demand  without  a  serious  restraint  upon 
the  progress  of  civiHzation. 

The  daily  quantity  required  for  each  person  has  increased 
from  the  two  to  four  gallons  drawn  by  bucket  from  the  farm- 
house w'ell  to  thirty  or  forty  gallons  taken  from  the  town  sup- 
ply bv  the  turning  of  a  faucet,  and  in  cities  where  much  is  used 
for  manufacturing  purposes,  for  running  elevators  and 
motors,  the  daily  amount  may  reach  lOO  gallons  per  inhabi- 
tant. This  constantly  increasing  use  of  water  for  other  than 
cleansing  purposes  has  enormously  increased  the  difificulty 
of  securing  clean  water  for  domestic  use.  Not  only  is  a 
larger  quantity  of  polluting  material  deposited  in  the  water, 
but  it  is  carried  farther  from  its  source  by  the  dilution. 
This  fact,  as  w^ell   as  the  demand  for  higher  standards  of 


avater:  source,  properties,  and  relation  to  life.  45 

purity,  has  made  the  abandonment  of  private  water-supphes 
a  necessity,  and  has  demanded  from  municipaHties  the  best 
scientific  knowledge  and  the  most  careful  supervision  of  the 
quality  of  the  public  supply. 

A  city  or  town  is  under  as  strict  obligation  to  furnish  a 
safe  supply  of  water  as  it  is  to  provide  safe  roads.  To  this 
end,  the  proper  construction  and  maintenance  of  reservoirs 
and  a  sufficient  poHce  surveillance  of  the  watershed  is  as  im- 
portant as  abundance  of  supply. 

Education  of  the  people  at  large  is  still  necessary,  not 
only  that  those  who  depend  in  whole  or  in  part  upon  springs 
and  wells  may  know  how  to  protect  themselves,  but  also  that 
the  necessary  cost  of  the  larger  public  (municipal)  supply 
may  be  cheerfully  paid  for  by  the  citizens. 

Leaving  out  of  the  present  discussion  such  considerations 
as  belong  only  to  the  engineer  and  specialist,  the  problem  of 
potable  water  will  be  treated  in  this  chapter  from  the  point 
of  view^  of  the  intelligent  citizen  and  educated  individual  who 
cannot  afiford  to  remain  ignorant  of  so  important  a  factor  in 
the  general  welfare.  The  reason  why  this  education  is  needed 
lies  in  the  fact  that  primitive  habits  of  thought,  influencing 
action  in  every-day  life,  survive  long  after  the  race  has  passed 
beyond  the  original  conditions.  In  no  respect  is  this  more 
true  than  in  regard  to  water. 

The  ideal  drinking-w-ater  of  most  persons  is  the  clear, 
■colorless,  sparkling  water  of  a  spring,  refreshing  in  its  cool- 
ness and  satisfying  the  aesthetic  sense  by  its  suggestion  of 
purity.  So  strong  a  hold  has  this  ideal  that  it  is  most  diffi- 
•cult  to  convince  the  average  person  that  any  water  which  has 
these  characteristics  can  be  other  than  wholesome  and,  con- 
versely, that  water  lacking  in  any  of  these  qualities  is  suitable 
for  human  consumption.     Early  man  drank  clear  cool  water 


46  AIR,    WATKR,    AND    FOOD. 

wherever  he  found  it.  If  there  was  not  a  spring  at  hand,  he 
scooped  out  a  hole  in  the  sand.  Pioneer  settlers  dug-  the 
well  as  near  the  kitchen  door  or  the  barnyard  as  they  could 
find  water,  with  a  blind  faith  in  the  protecting  power  of 
mother  earth,  not  wholly  misplaced  so  long  as  the  require- 
ments of  the  household  did  not  exceed  two  or  three  gallons 
per  person  daily,  and  so  long  as  the  nearest  neighbor  was 
half  a  mile  away.  So  persistent  is  this  confidence  in  nature 
that  in  the  light  of  this  day  a  majority  of  intelligent  people, 
even,  will  quaff  at  a  roadside  well  or  drink  freely  at  a  count ly 
hotel  or  go  to  live  in  a  city  without  ever  taking  thought  for 
the  quality  of  the  water.  Water  is  water,  and  he  who  pauses 
with  his  glass  half-way  and  asks  whence  cOmes  the  supply  is 
scouted  as  a  weak-minded  crank.  So,  too,  when  town  au- 
thorities have  spared  no  pains  or  expense  to  secure  a  safe 
supply  from  a  distant  lake,  and  have  guarded  it  by  all  means 
known  to  science,  the  primitive  habit  of  thought,  requiring 
colorless  water  of  an  even  coolness  of  temperature  leads 
those  who  can  afford  it  to  purchase  "  spring  "-water  in  jugs 
and  bottles,  with  the  blind  faith  of  the  savage  that  what  comes 
out  of  the  ground  must  be  good. 

Fundamental  race-habits  are  taken  advantage  of  by  the 
dealer  in  spring-waters  as  well  as  by  the  vendor  of  patent 
medicines — the  missionary  has  no  chance  against  him. 
From  the  schools  and  colleges  there  should,  however, 
be  sent  out  a  generation  of  more  intelligent  persons  who,, 
learning  to  weigh  evidence,  will  not  take  chances  and 
will  help  to  develop  a  public  opinion  on  sanitary  matters, 
especially  in  regard  to  water-supplies.  For  not  until 
there  is  an  intelligent  public  can  the  present  reckless  use  of 
water  and  ground  be  stopped.  While  not  every  man  may 
be  a  chemist,  he  can  have  that  modicum  of  knowledge  which 
will  enable  him  to  understand  the  need  of  chemical  tests  of 


water:  source,  properties,  and  relation  to  life.  47 

water  and  to  distinguish  between  the  work  of  the  expert  and 
the  amateur. 

However  safe  this  ideal  of  clear,  colorless  water  may  have 
been  in  early  times,  it  must  now  be  relegated,  with  the  un- 
barred door  and  unwatched  treasure,  to  the  mountain  fast- 
nesses. As  the  country  becomes  settled,  appearance  and 
taste  are  no  longer  sufficient  guides;  therefore  scientific  tests 
must  be  applied  and  the  results  interpreted  by  trained  ob- 
servers to  whom  the  individual  subordinates  his  private 
judgment. 

The  ideal  water  should  be  above  suspicion,  for  if  it  has 
once  been  contaminated,  who  can  tell  how  soon  it  will  find 
bad  company  again?  Not  the  analyst  in  his  laboratory.  In 
fact,  the  laboratory  verdict  is  worth  very  little  without  a 
knowledge  of  outside  conditions  and  without  a  keen  detec- 
tive insight  which  scents  out  the  most  unlikely  causes. 
Nevertheless  the  evidence  given  by  analytical  results  is 
needed  to  procure  conviction. 

Although  "  pure  "  water  is  found  only  in  the  laboratory, 
"  safe  "  water,  that  which  is  reasonably  free  from  objection- 
able substances,  mineral  and  organic,  may  be  obtained  with 
sufficient  care  and  knowledge. 

A  clear  understanding  of  the  problem  requires  a  close 
study  of  the  circulation  of  water  on  the  earth.  Let  us  trace 
the  course  of  water  from  sky  to  ocean,  in  view  of  its  availa- 
bility for  domestic  use,  and  note  the  dangerous  properties  it 
may  acquire,  considering  also  the  changes  in  condition  which 
it  may  undergo  in  its  course  from  mountain  to  sea. 

Water-vapor  rising  from  sea  and  land  is  condensed  in  the 
upper  air,  then  falls  to  the  earth,  absorbing,  as  it  does  so, 
ammonia,  carbon  dioxide,  sulphur  oxides,  and  other  soluble 
gases,  if  present,  and  washing  the  air  free  from  dust-particles, 
mineral  and  organic. 


48  AIR,    WATKR,    AND    FOOD. 

This  meteoric  water  (rain  or  snow),  although  nearly  free 
from  dissolved  mineral  substances,  is  therefore  by  no  means 
pure.  Furthermore,  rain  falling  on  insoluble  rocks,  bare  or 
lichen-covered,  or  on  loose,  sandy  soils,  washes  them  also, 
giving  up  to  the  vegetation  the  ammonia  and  taking  in  re- 
turn carbon  dioxide  and  dissolved  albuminoid  ammonia. 

Water  thus  enriched  has  increased  solvent  power  on  cer- 
tain rocks  and  soils.  This  rain-water  soon  forms  rivulets 
which, passing  down  from  the  highlands  into  the  forest, spread 
over  the  moss-covered  area,  soaking  the  leaves  and  peaty  soil 
and  extracting  organic  substances.  Mountain  brooks,  as  well 
as  lowland  streams,  draining  a  region  free  from  limestone,  are 
thus  colored  brownish-yellow  and  furnish  "  meadow-tea,"  as 
Thoreau  happily  named  it.  As  the  stream  flows  on  it  re- 
ceives contributions  of  many  kinds — the  overflow  of  springs, 
the  under-drainage  from  cultivated  fields,  the  surface-wash 
from  pasture  and  meadow.  Scavengers  are,  however,  con- 
stantly at  work.  Brought  as  dust  by  the  ever-passing  air- 
currents,  seeds  of  tiny  plants  freely  sprout  in  the  w^ater  and 
grow  rapidly  whenever  a  quiet  pool  or  lake  gives  oppor- 
tunitv.  The  products  of  organic  decay  and  the  ammonia  of 
the  rain  may  be  thus  removed  and  the  water  pass  on  to  the 
reservoir  clear  and  soft  and  as  nearly  pure  as  nature  furnishes. 
It  is,  however,  becoming  rare  to  find  even  a  mountain  stream 
or  forest  brook  which  has  not  been  subjected  to  modification 
bv  human  agencies.  Three  kinds  of  contamination  may  take 
place.  First:  A  farmhouse  high  up  on  the  hillside  lays  trib- 
ute for  drinking  purposes  upon  that  water  finding  its  way 
beneath  the  sand  which  appears  in  the  form  of  a  spring.  The 
overflow  is  made  into  a  duck-pond,  or  passes  through  the 
watering-trough  by  the  roadside  before  it  joins  other  water 
tumbling  over  the  rocks  as  a  rapid  stream.  The  brook  thus 
grown  larger  widens  out  a  little  below  the  farmhouse  into  a 


water:  source,  properties,  and  relation  to  life.  49 

shallow  pool,  in  which  one  or  two  cows  frequently  seek  com- 
fort. The  water  has  become  rich  in  organic  matter  and  sup- 
ports a  thick  growth  of  tiny  plants;  the  stones,  even,  may  be 
coated  with  green  slime.  This  vegetation  serves  as  a  warning 
to  the  hunter  and  the  woodsman,  who  wisely  drink  only  of 
water  from  clear  pools  with  bottom  of  shining  sand.  The 
heavy  material  stirred  up  by  the  cattle  soon  settles,  leaving 
the  water  in  the  stream  below  clear,  although  probably  a  little 
yellow  in  color.  It  still  tastes  well  and  looks  all  right,  and 
may  be  used  by  human  beings  with  probable  impunity. 

Second:  The  little  stream  next  passes  other  farm  build- 
ings, where  the  privy  is  put  over  it  to  save  the  trouble  of 
cleaning,  or,  even  if  not  so  close,  is  placed  in  such  a  way  as  to 
allow  of  a  possible  wash  into  it,  especially  in  times  of  sudden 
rain. 

A  case  of  typhoid  fever  develops  at  this  farm.  No  pre- 
caution is  taken  to  disinfect  the  discharges,  and  a  portion  of 
the  dangerous  material  is  carried  into  and  along  with  the 
water.  Some  two  or  three  miles  below,  another  farmhouse, 
having  no  spring,  uses  this  same  little  stream  for  its  supply, 
perhaps  damming  it  up  into  a  little  pond  or  pumping  it  into 
a  tank.  All  unconscious  of  what  has  happened  above,  or 
ignorant  of  consequences,  this  water  with  a  history  is  freely 
used,  and  perhaps  the  whole  family  come  down  with  the  dis- 
ease, perhaps  only  the  delicate  one  may  have  it.  It  may  be 
that  they  will  all  escape,  owing  to  the  fact  that  they  were 
particularly  robust,  or  that  they  drank  no  water  raw,  or  that 
the  conditions  on  the  stream  have  been  favorable  to  purifica- 
tion of  the  water  by  storage  and  consequent  growth  of  the 
green  plants,  which  are  our  friends  in  such  cases;  but  if  the 
water  were  pumped  into  a  covered  tank  and  used  soon  after, 
the  chances  are  nine  to  one  that  some  deleterious  results 
followed. 


50  AIR,    WATKR,    AM)    FOOD. 

Third:  A  part  of  the  water  sinks  throus^h  the  sand,  and  by 
this  filtration  becomes  freed  from  all  suspended  matter  and 
consequently  from  the  germs  of  disease,  if  present.  In  its 
course  if  it  is  intercepted  and  collected  in  a  shallow  well  it 
may  again  be  of  great  organic  purity  and  free  from  danger, 
but  it  will  surely  bear  the  telltale  marks  of  its  progress  in 
the  increase  of  chlorine  and  solids  wdiich  will  have  escaped 
all  the  agents  of  purification,  and  in  the  nitrates,  the  result  of 
the  process. 

It  will  be  noticed  that  it  is  only  after  contamination  with 
the  "  ivastc  of  human  life  "  that  danger  comes  to  other  human 
beings  and  that  many  circumstances  modify  that  danger. 
The  chances  are  about  equal  to  those  of  fire;  and  as  most 
householders  think  it  worth  while  to  insure  against  possible 
fire,  so  they  should  hold  the  chemist's  certificate  as  a  sort  of 
water  insurance;  but  since  the  fire  policy  does  not  protect 
from  carelessness,  the  knowledge  that  the  water-supply  is 
once  good  does  not  absolve  the  householder  or  the  citizen 
from  the  greatest  care  in  protecting  his  premises.  Duty  to 
his  neighbor  should  lead  him  to  see  that  this  coin  of  the 
world  is  passed  on  in  as  good  condition  as  possible,  and  he 
should  at  least  give  notice  of  danger  when  he  knows  that  it 
exists. 

But  this  general  movement  of  w^ater  on  and  near  the  sur- 
face is  not  all  the  story.  From  25  to  40  per  cent,  of  the 
annual  rainfall,  in  temperate  regions,  soaks  at  once  into  the 
ground,  and  passing  downward  through  the  soil  to  hard-pan, 
to  clayey  or  impervious  layers,  or  to  rock  surface,  thence 
through  crevices,  broken  joints,  or  glacial  drift-deposits  to 
the  water-table,  flows  along  the  slope  for  many  miles,  until 
it  finds  its  way  again  to  the  surface,  either  from  the  bottom 
of  a  lake,  the  bed  of  a  river,  the  side  of  a  hill,  supplying  wells 
or  appearing  as  a  spring  free  from  all  organic  and  suspended 


water:    source,  troperties,  and  relation  to  life.  5r 

matter  but  often  rich  in  gases.  In  any  one  of  these  courses 
it  may  be  intercepted  by  man  and  caught  or  pumped  for  his 
use.  Such  water  may  never  have  been  far  from  the  surface; 
it  may  have  been  used  and  returned  to  the  ground  many 
times;  it  may  have  appeared  as  surface-water  and  again  dis- 
appeared to  great  depths.  It  has  been  estimated  that  water 
moves  in  the  ground  at  rates  varying  from  0.2  to  20  feet  per 
day.  This  long  contact  with  rocks  will,  of  course,  bring  min- 
eral substances  into  solution  which  may  be  precipitated  as 
new  rocks  are  reached  or  other  streams  encountered,  so  that 
the  same  gallon  of  water  may  have  had  many  stages  in  its 
course  and  may  have  held  many  different  substances  in  solu- 
tion. An  example  of  how  much  can  be  so  held  is  found  in 
the  waters  of  the  alkali  belt  (page  199). 

It  is  no  wonder  that  so  active  a  solvent  as  water  should 
take  with  it  much  substance  whenever  it  remains  long  in  con- 
tact with  soil  or  rock,  for  it  may  be  many  months  before  that 
which  has  once  sunk  out  of  sight  again  appears.  In  fact,  great 
rivers  are  supposed  to  flow  into  the  sea  from  under  the  sur- 
face. 

Then,  too,  the  acquisition  of  dissolved  gases  favors  the 
solution  of  many  substances;  for  instance,  water  carrying- 
carbon  dioxide  dissolves  limestone  as  well  as  lead  and  cop- 
per, and  when  at  low  temperature  and  containing  ammo- 
nium carbonate  water  may  dissolve  ferric  iron. 

Water  carrying  organic  acids  dissolves  among  other  sub- 
stances iron  compounds  which  may  or  may  not  be  in  the 
ferrous  condition,  and  therefore  may  or  may  nbt  be  precipi- 
tated on  coming  to  the  surface.  And  as  we  have  seen  that 
the  ground  below  a  certain  level  is  permeated  with  moving- 
water,  whatever  is  buried  in  the  earth  is  likewise  liable  to  enter 
the  watercourses  in  one  form  or  another. 

An   understanding   of   this   movement   of  water   under- 


52  AIR,    WATER,    AND    FOOD. 

ground,  with  the  accompanying  changes  in  its  character, 
cannot  be  too  strongly  insisted  upon,  for  the  lack  of  com- 
prehension of  it  is  at  the  root  of  most  of  the  troubles  from 
\v'ell-waters.  For  example,  the  leaching  cesspool,  the  primi- 
tive "  septic  tank,"  delivers  its  more  or  less  filtered  water  rich 
in  nitrogen  compounds  into  the  general  circulation  at  a 
depth  below  the  most  efificient  action  of  the  nitrifying  or- 
ganisms, hence  it  may  permit  the  passage  of  organisms  of 
putrefaction  into  underground  streams  or  into  the  A\ell,  when 
access  is  direct.  Even  when  filtration  is  perfect,  the  products 
of  decay  are  yet  carried  with  it  and  so  tell  the  story  of  the 
past.  The  difficulty  is  to  determine  the  state  of  the  filter 
which  may  be  on  a  neighbor's  land  many  hundred  feet  away, 
and  to  be  sure  that  its  action  is  uniform.  Experience  with 
artificial  filters  shows  how  difficult  it  is  to  maintain  efficiency 
with  rapid  use;  hence  heavy  rains  or  wet  years  may  cause  a 
state  of  danger  not  ordinarily  existing. 

The  relation  of  water  to  human  health  must  be  consid- 
ered chiefly  in  the  light  of  the  changes  which  go  on  in  the 
substances  held  suspended  or  dissolved  in  it,  and  the  effect 
of  these  changes  on  the  wholesomeness  of  the  water.  The 
suspended  matter  may  be  either  inert,  as  clay  or  sand;  dead 
vegetable,  as  fragments  of  plants;  living  vegetable,  as  plants 
floating  on  the  surface,  diatoms,  desmids,  algae,  etc.;  dead  or 
living  animal,  as  infusoria,  small  crustaceans,  etc. 

Wherever  these  occur  there  are  found  the  lower  orders 
of  vegetable  organisms,  fungi,  moulds,  bacteria,  ready  to  do 
the  necessary'  work  of  decomposition  preparatory  to  solu- 
tion. The  mere  presence  of  these  forms  of  living  matter 
does  not  of  itself  mean  danger  to  those  using  the  water,  but 
among  these  may  be  found  pathogenic  organisms  which  are, 
at  present,  considered  as  liable  to  cause  disease.  Such  mi- 
crobes do  not  find  in  water  a  congenial  habitat,  and,  fortu- 


water:    source,  properties,  and  relation  to  life.  53 

nately,  do  not  thrive  on  the  vegetable  diet  and  in  the  cool  tem- 
perature of  natural  waters,  hence  the  other  organisms  soon 
overpower  them;  danger  decreases  not  only  in  proportion  to 
distance,  time,  and  dilution,  but  also,  probably,  to  the  abun- 
dance of  other  vegetable  life.  Under  favorable  circum- 
stances the  danger  is,  however,  a  very  real  one. 

The  presence  of  certain  living  plants  may,  moreover,  give 
rise  to  unpleasant,  if  not  dangerous,  tastes  and  odors,  due  to 
the  presence  of  extremely  pungent  oils  or  other  aromatic 
substances  formed  in  the  process  of  growth.  AMien  these 
plants  are  decaying  putrefactive  odors  are  also  present,  some- 
times rendering  the  water  too  offensive  for  use.  These  or- 
ganisms are  described  in  Whipple's  ''  Microscopy  of  Drink- 
ing-water," and  in  Chapter  \TI  a  short  list  of  those  which 
give  characteristic  odors  will  be  found. 

The  presence  of  much  decaying  vegetable  matter  in 
drinking-water  is  to  be  avoided,  since  it  is  not  known  what 
effect  it  may  have  upon  the  general  health  of  the  individual, 
rendering  him  perhaps  more  susceptible  to  disease. 

Food-supply  is  a  necessary  condition  for  life,  and  there 
cannot  be  abundant  growth  in  a  water  without  a  correspond- 
ingly large  amount  of  dissolved  substances  furnishing  the  food 
for  this  living  fauna  and  flora.  As  has  been  stated,  water 
usually  carries  considerable  mineral  substance  and  is  often 
supplied  with  organic  and  gaseous  compounds,  while  nitro- 
gen is  furnished  from  many  sources,  most  abundantlv  from 
sewage,  so  that  it  is  not  strange  that  water-life  is  so  abundant, 
but  rather  that  it  is  not  more  so.-  Most  of  the  difificulties  in 
securing  a  satisfactory  water-supply  are  connected  with  the 
cycle  of  nitrogen  in  its  relation  to  organic  life. 

This  may  be  briefly  stated  as  follows:  Nitrogen  is  found 
as  an  essential  constituent  of  all  living  matter.  When  ihns 
combined,  it  is  the  so-called  organic  nitrogen,  and  is  found 


54  AIR,    WATER,    AND    FOOD. 

in  undecomposed  vegetable  or  animal  substances.  As  soon  as 
dead,  these  substances  may  become  food  for  micro-organisms 
and  the  nitrogen  then  appears  in  a  form  from  which  it  can  be 
obtained  as  ammonia;  for  instance,  from  decaying  beans,  from 
putrefying  broth,  and  from  fresh  sewage.  This  process  takes 
place  with  or  without  much  air  and  may  be  accompanied  by 
very  bad  odors.  As  soon,  however,  as  the  nitrogen  has  passed 
from  the  insoluble  organic  form  into  the  soluble  compounds 
from  which  ammonia  is  obtained,  then,  if  oxygen  is  present, 
and  only  then,  another  set  of  micro-organisms  take  up  the 
work  and  nitrites  appear;  when  still  another  set  have  done 
their  work  the  nitrogen  is  found  only  in  combination  as  ni- 
trates, fully  oxidized  and  mineralized,  no  longer  organic  or 
■capable  of  sustaining  the  life  of  the  lower  forms  of  vegetation, 
hut. on  the  other  hand, the  most  valuable  food  for  chlorophyll- 
bearing  plants  which  convert  nitrates  again  into  organic 
nitrogen.  This  cycle  may  be  arrested  or  broken  at  certain 
stages.  If  the  soluble  ammonia  compounds  are  set  free  out 
of  contact  with  air  or  below  the  layers  of  soil  containing  the 
nitrifying  organisms,  they  may  remain  indefinitely  un- 
changed. If  nitrates  have  been  carried  below  the  reach  of 
the  roots  of  the  chlorophyll-bearing  plants,  or  if  they  are  con- 
iined  in  a  space  deficient  in  oxygen,  then  an  access  of  decom- 
posable organic  matter  with  micro-organisms  will  cause  a 
reduction  of  the  nitrates  to  nitrites  and  free  nitrogen,  through 
the  action  of  these  lower  plants  which,  in  the  absence  of 
air,  take  the  little  oxygen  they  need  from  mineral  com- 
pounds. 

These  micro-organisms  are  not  the  only  ones  at  work, 
however.  In  any  sudden  prominence  of  one  factor  others 
are  apt  to  be  overlooked;  thus  in  the  present  case  the  in- 
finitely small  has  so  powerfullv  affected  men's  minds  that, 
jDartly  because  the  micro-organisms  are  beyond  their  range 


AVATER:     SOURCE,    PROPERTIES,    AND    RELATION   TO    LIFE.    55 

of  vi-sion,  such  forms  of  life  as  are  evident  to  the  naked  eye 
or  with  low  powers  of  the  microscope  have  been  overlooked 
to  an  extent. 

As  agents  of  putrefaction  and  of  decay  the  micro-organ- 
isms have  their  work  to  do,  but  the  final  purification — the 
finishing  up  of  the  work — belongs  to  another  order  of  life. 
The  still  minute  but  visible  green  plants — those  which  f^oat 
free  in  water  or  attach  themselves  to  larger  growths — have 
now  their  part  to  play.  The  life-history  of  these  forms  has 
been  little  studied,  and  the  work  they  do  in  the  actual  puri- 
fying of  polluted  water  has  been  almost  overlooked.  The 
impression  left  on  reading  most  books  is  that  when  foul  m.at- 
ter  has  been  dissolved  and  converted  into  ammonia,  carbon 
dioxide,  and  nitrates  the  work  is  done,  but  these  compounds 
only  furnish  food  for  the  next  class,  and  these  again  for  in- 
fusoria, tiny  crustaceans,  etc. 

In  some  cases  these  organisms  succeed  each  other  with 
great  rapidity;  in  one  case  the  fauna  and  flora  of  a  given 
pond  varied  each  week  of  a  season,  certain  rare  forms  being 
found  only  once. 

There  is  needed,  almost  more  than  anything  else,  a  con- 
secutive study  of  the  green  plants  found  in  water-supplies. 
since  by  their  cultivation  greater  purity  might  be  attained 
and  possibly  a  w^ay  might  be  found  of  exterminating  the  dis- 
agreeable ones.  The  most  unexpected  results  may  follow 
the  long  study  of  a  single  organism,  such  as  has  been  given 
to  Oscillaria  prolifica  of  Jamaica  Pond  for  a  period  of  eleven 
years.  Weekly,  sometimes  daily,  observations  have  been 
made  for  two  or  three  years.* 

It  is  organisms  of  this  class  which  give  tastes  and  odors 
to  water,  and  which,  if  enough  were  known  concerning  them, 

*  Trans.  A.  A.  A.  S.,  1898. 


56  AIR,    WATER,    AND    FOOD. 

would  probably  give  perfectly  trustworthy  evidence  as  to  the 
past  history  or  source  of  contamination. 

The  two  classes  of  organisms  work  in  opposite  directions, 
and  so  long  as  food  is  present  for  either,  life  will  increase  with 
proportional  rapidity.  This  connection  of  cause  and  effect 
should  be  made  familiar  to  the  intelligent  citizen.  When  a 
ground-water  free  from  all  organic  matter  but  rich  in 
nitrates  is  exposed  in  an  open  basin  the  rich  growth  of 
chlorophyll-bearing  algic  follows  as  a  matter  of  course;  later,, 
decay  sets  in  and  products  of  decomposition  abound,  the  air 
above  being  the  source  of  a  constant  supply  of  spores  of  all 
kinds. 

When  a  house-  or  barn-drain  empties  into  a  small  slug- 
gish stream,  it  soon  becomes  filled  with  green  plants  thriving 
on  the  ammonia,  and  it  is  often  possible  to  trace  the  source 
of  pollution  of  a  large  lake  by  the  line  of  green  anabcxna 
leading  to  the  insignificant  ditch. 

A  curious  blindness  on  the  part  of  managers  of  water- 
works to  the  movements  of  water  and  its  action  in  transport- 
ing material  is  seen  not  only  in  the  almost  universal  proximity 
of  cemeteries  to  reservoirs,  but  also  in  the  common  practice 
of  dressing  the  sloping  banks  of  turf  with  a  heavy  coating  of 
manure.  Even  if  this  was  derived  from  clean  stables  and 
was  not  liable  to  be  contaminated  with  night-soil,  the  abun- 
dant food  for  plants  which  inevitably  finds  its  way  into  the 
reservoir  occasions  as  fruitful  results  in  the  water  as  on  the 
banks,  and  is  undoubtedly  the  cause  of  much  of  the  trouble 
in  storage  basins. 

It  is  evident,  therefore,  that  a  once  polluted  water  cannot 
be  said  to  be  purified  so  long  as  food  for  green  plan*^s  re- 
mains, for  the  moment  the  temperature  and  other  conditions 
become  favorable  growth  will  begin.  The  term  "  purifica- 
tion," taken  in  a  chemical  sense,  should  not  be  loosely  used. 


ayater:    source,  properties,  and  relation  to  life.  57 

Complete  puritication  can  take  place  only  when  all  traces  of 
former  impurity,  in  any  form,  have  been  removed.  Chemical 
precipitation  of  sewage  leaves  the  soluble  ammonia,  and  sand 
filtration  leaves  nitrates  to  serve  for  abundant  life  and  sub- 
sequent decay  in  the  streams  into  which  the  effluents  flow. 
Such  efBuents  are  clariiied  and  the  organic  matter  may  have 
been  mineralized,  but  this  is  not  purified  water.  Only  when 
growing  plants  have  removed  this  food  and  have  themselves 
been  removed  can  the  water  approach  a  purified  condition. 

The  eft'ect  of  storage  of  water  containing  high  nitrates 
in  open  tanks  or  reservoirs  exposed  to  the  collection  of  dust 
will  be  that  spores  of  chlorophyll-bearing  algce,  diatoms, 
desmids,  etc.,  will  soon  develop  and  will  increase  as  long, as 
the  food  (nitrates,  mineral  matter,  etc.)  lasts.  Only  by  pro^ 
tection  from  dust  and  light  can  such  water  be  kept  free 
from  unpleasant  accumulations  of  suspended  organisms  or 
from  disagreeable  tastes.  Unpolluted  surface-waters,  on  the 
other  hand,  improve  on  storage,  as  a  general  rule,  if  the  basin 
is  a  clean  one.  The  storage  of  polluted  or  clarified  water  is 
thus  forbidden,  since  not  infrequently  the  first  indication  of 
the  pollution  of  a  surface  supply  is  given  by  the  appearance 
of  some  member  of  that  richly  nitrogenous  group  of  algae 
called  cyanophycece,  or  "  blue- greens/'  from  the  presence  of 
blue  or  purple  coloring  matter  along  with  the  yellow-green 
chlorophyll.  Since  this  group  of  plants  contains  from  seven 
to  eleven  per  cent,  of  nitrogen,  while  other  groups  contain 
only  one  or  two,  it  is  evident  that,  if  it  is  to  flourish,  more 
nitrogenous  food  must  be  supplied.  This  may  be  derived 
from  fertilized  fields,  from  decav  of  other  vegetable  life,  as 
well  as  from  the  richer  source  of  direct  sewage;  but,  in  any 
case,  the  growth  of  these  plants  is  a  sign  of  abundant  food- 
supply  which  must  be  cut  off  if  they  are  to  be  starved  out,  as 
thev  must  be  unless  they  arc  removed  while  fresh  by  strain- 


58  AlK,    WATER,    AND    FOOD. 

ing  or  skimming,  for  the  odor  of  their  decay  is  so  intolerable 
as  to  preclude  the  use  of  the  water.  In  some  cases  the  odor 
accompanying  their  growth  renders  the  water  quite  objec- 
tionable, and  neither  natural  nor  artificial  filtration  is  able  to 
remove  it. 

Either  natural  or  artificial  basins  may  have  a  collection  of 
vegetable  matter  on  the  bottom  which  slowly  decomposes 
in  summer,  and  since  the  bottom  water  is  colder,  the  resulting 
ammonia  remains  until  the  late  fall  overturn,  when  it  is 
brought  to  the  surface,  where  it  favors  the  growth  of  diatoms 
and  other  cold-water  plants.  Certain  diatoms,  as  asterio- 
nella,  cause  disagreeable  odors.  Such  basins  show  the  least 
ammonia  in  early  October  and  the  most  in  late  November. 

In  order  to  make  any  predictions  as  to  the  prc'bable  de- 
velopment of  this  flora  and  fauna  of  water,  experience  and 
at  least  a  year's  watching  of  any  given  supply  are  required 
until  more  is  knowai  of  the  life-history  of  these  forms  of  life. 
Nothing  is  more  needed  to-day  than  work  along  these  lines. 
When  may  disagreeable  odors  and  tastes  be  expected? 
What  precaution  or  measures  may  be  taken  in  each  case  to 
prevent  them?  These  are  the  questions  the  water-works 
superintendent,  equally  with  the  consumer,  is  asking,  for  the 
most  part  vainly  as  yet. 

As  has  been  stated,  surface-w^aters  often  carry  stable  or- 
gfanic  matter  in  connection  with  color,  so  that  while  the 
organic  nitrogen  show^s  high,  no  free  ammonia  or  nitrates  are 
formed  on  standing.  These  weak  meadow-teas  are  now 
largely  used  for  tow-n  supplies,  and  a  w'ord  as  to  the  source 
of  the  color  may  not  be  amiss.  Many  carbonaceous  sub- 
stances, sugar,  for  example,  when  partially  broken  up  become 
caramelized  and  give  a  brown  solution,  the  color  being  due 
to  substances  richer  in  carbon;  this  color  is  deeper  as  th2 
decomposition  is  more  complete.     There  is  no  reason  to  sup- 


water:   source,  properties,  and  relation  to  life.  59 

pose  that  such  compounds  have  any  deleterious  effect  on 
health.  Indeed,  experience  has  proved  that  such  waters  are 
more  reliable  than  many  others. 

The  chlorine  of  unpolluted  natural  waters  is  derived  from 
the  sea  in  past  or  present  times.  Waves  breaking  on  a 
rocky  shore  send  finely  divided  salt-spray  high  into  the  air; 
dust-particles  becoming  coated  with  it  carry  their  burden  of 
salt  around  the  world.  The  rain  brings  to  earth  now  more, 
now  less  of  this  salted  dust,  each  region  receiving  in  the 
course  of  the  year  an  amount  fairly  proportional  to  its  dis- 
tance from  the  seacoast  and  to  the  rainfall.  No  mountain 
lake  or  stream  has  yet  been  found  free  from  this  element. 
Where  evaporation  and  rainfall  nearly  balance,  the  normal 
chlorine  will  be  that  of  the  rain  for  the  year,  but  where  evapo- 
ration is  in  excess  it  may  exceed  that  for  any  given  year.  In 
the  absence  of  salt-springs  and  industries  using  much  salt, 
the  source  of  chlorine  in  excess  of  the  normal  is  the  do- 
mestic life  of  man.  Mr.  F.  P.  Stearns  has  estimated  that  the 
chlorine  in  the  drainage  of  any  watershed  is  increased  one- 
tenth  part  per  million  by  20  inhabitants. 

Chlorine  may  serve  to  prove  not  only  the  presence  but 
the  amount  of  sewage  pollution  in  any  case  where  the  other 
factors  are  known.  Otherwise  chlorine  has  no  sanitary 
significance. 

Of  the  mineral  constituents  in  waters  there  is  little  to 
say  except  that,  like  climate,  water  is  to  be  taken  as  it  is 
found — hard,  high  in  mineral  matters  if  derived  from  a  lime- 
stone region,  soft  if  from  archean  formations.  Physicians  are 
not  agreed  as  to  the  effects  of  hard  water,  or  of  the  brown 
soft  waters. 

Fortunately  the  human  system  possesses  remarkable 
adaptability,  so  that  if  slowly  accustomed  to  a  given  condi- 
tion, as  we  have  seen  in  the  case  of  air,  and  as  we  shall  have 


6o  AIR,    WATER,    AND    FOOD. 

occasion  to  remark  when  food  is  considered,  it  can  safely 
bear  what  would  be  a  serious  shock  if  suddenly  encountered 
from  an  opposite  condition.  Natives  of  a  hard-water  region 
are  made  ill  on  coming  to  a  soft-water  region,  and  vice  versa. 
Inhabitants  of  a  city  with  a  polluted  water-supply  seem  to 
acquire  a  certain  immunity. 

The  safety  from  organic  contamination  secured  by  the 
use  of  distilled  water  has  brought  up  the  question  of  a  pos- 
sible danger  in  too  little  mineral  contents  for  the  best  cellular 
interchange  wherein  lies  life. 

With  the  superabundance  of  mineral  salts  in  ordinary 
diet,  there  would  seem  to  be  little  cause  for  alarm;  but  if  the 
food  were  poor  in  these  substances,  it  is  quite  conceivable 
that  evil  results  might  follow  a  free  use  of  distilled  water. 

A  word  as  to  the  care  of  water  in  the  house  may  not 
seem  amiss,  in  view  of  the  tendency  it  has  to  absorb  gases, 
to  collect  dust,  to  favor  chemical  and  vital  changes,  to  dis- 
solve metals. 

Too  great  care  cannot  be  taken  in  all  these  directions  to 
secure  water  freshly  drawn  from  the  main  pipe  beyond  the 
lead  or  brass  house-pipes  and  to  avoid  those  traps  for  the  un- 
wary householders — faucet  filters. 

When  the  water-supply  is  cafe,  but  warm  and  flat  to  the 
taste,  ice  is  frequently  used  to  cool  it. 

Much  has  been  said  about  the  dangers  of  ice  when  used 
in  drinking-water  and  on  or  about  food.  The  latter  is  prob- 
ably the  most  serious  danger,  since  people  are  not  so  careful 
about  the  quality  of  ice  for  that  purpose. 

Certain  rules  may  be  broadly  stated  as  guides  to  the 
householder: 

Crystal-clear  ice,  free  from  crevices,  bubbles,  etc.,  is 
probably  pure,  for  it  has  been  formed  from  slow  freezing  in 
a  thin  layer,  over  a  deep  mass  of  water,  as  20  to  30  inches  of 


r/^».     V  cr- 


m 


-m 


^^ 


r.: 


\^1^' 


>^ 


^ 


per 


^  \    C  A  P  £         C  C   ( 


STATE  BOARD  OF  HELALTH 
MAP  OF  THE 

STAI'E  OF  MASSACHUSETTS.  ^^^^ 

SHOWING 

NORMAL  CHLORINE. 


water:  source,  properties,  and  relation  to  life.  6 1 

ice  in  a  pond  40  or  60  feet  deep.  In  this  case  the  impuri- 
ties have  been  excluded.  This  crystal  ice  is  impermeable  to 
air  and  therefore  to  what  air  carries,  and  of  course  to  water 
and  what  it  carries. 

An  equally  safe  rule  is  to  discard  all  "  snow-ice  "  made 
from  snow  saturated  with  water. 


CHAPTER  VI. 

THE    PROBLEM    OF    SAFE    AND    ACCEPTABLE    WATER    AND    THE 
INTERPRETATION    OF    ANALYSES. 

{From  the  Chemist's  Standpoint.) 

From  what  has  been  said  it  will  be  evident  that  the  prob- 
lem of  safe  water  for  domestic  use  is  not  so  much  concerned 
with  the  water  itself  as  with  its  property  as  a  carrier  and  its 
part  in  chemical  changes. 

We  have  seen  how  a  great  variety  of  vegetable  and  ani- 
mal matter  finds  its  way  into  the  water  of  a  settled  region; 
and  as  it  is  constantly  being  transformed  from  one  form  to 
another  by  the  agency  of  multitudes  of  organisms,  it  is  evi- 
dent that  the  exigencies  of  modern  life  render  impossible  the 
exclusive  use  of  water  of  great  organic  purity.  It  is  useless, 
therefore,  to  fight  over  again  the  battles  of  the  past  as  to  the 
source  and  kind  of  "  organic  matter  "  in  water. 

We  have  also  seen  that  it  is  not  the  mere  presence  of 
compounds  of  carbon,  hydrogen,  and  nitrogen  in  drinking- 
water  which  gives  the  element  of  danger.  It  is  not  even 
the  fact  that  these  have  taken  part  in  animal  life;  fish  and 
frogs  continually  die  in  ponds  and  streams,  to  say  nothing 
of  countless  cyclops  and  mosquito  larvae.  Well  authenti- 
cated cases  are  on  record  in  which  one  drink  of  a  polluted 
water  has  proved  fatal;  while,  on  the  other  hand,  it  is  equally 
sure  that  highly  contaminated  water  has  been  used  with  ap- 
parent impunity. 

62 


water:   the  problem  of  safe  water.  63 

When  water  has  received  excreta  of  diseased  human 
beings,  disease-germs  are  very  Hkely  to  be  conveyed  by  it 
to  other  human  beings.  In  a  city  there  are  always  cases  of 
disease,  therefore  aU  city  sewage  is  to  be  considered  danger- 
ous. But  besides  the  Hving  germs  there  are  other  accom- 
paniments of  decaying  organic  matter  which,  when  in  con- 
centrated form,  sometimes  show  toxic  properties.  Certain 
facts  and  many  conjectures  lead  to  the  conclusion  that  a 
water  is  "  safe  "  only  when  free  from  decaying  substances. 

Along  with  the  millions  of  harmless  micro-organisms 
engaged  in  the  work  of  conversion  there  may  be  a  few  score 
inimical  to  the  health  of  man,  and  for  the  education  of  the 
still  skeptical  public  it  is  often  advisable  to  speak  somewhat 
strongly  of  the  possible  dangers  from  water-borne  disease- 
germs. 

Nitrogen  as  flic  Essential  Element  in  Living  Matter. — All 
organisms  from  the  lowest  to  the  highest  thrive  only  in  the 
presence  of  food;  therefore  only  that  organic  matter  which 
serves  to  support  life  or  which,  as  a  product  of  life,  may  be 
deleterious  to  man  is  rightly  to  be  held  as  dangerous.  The 
element  common  to  both  kinds  is  nitrogen;  therefore  the 
water-analyst  seeks  evidence  not  only  of  its  presence  or  ab- 
sence, but  of  the  forms  in  which  it  is  found  and  their  relation 
to  one  another.  It  may  be  assumed  that  any  water  which 
shows  no  change  in  the  relative  amount  of  its  nitrogenous 
compounds  at  the  end  of  a  week  either  does  not  contain  the 
organisms  necessary  to  effect  this  change  or  is  wanting  in 
the  food  upon  which  they  can  thrive.  As,  however,  it  is 
inconvenient  to  wait  a  week  before  deciding  this  point,  other 
methods  are  used.  The  so-called  albuminoid  ammonia  is 
supposed  to  indicate  the  amount  of  decomposable  nitrogen- 
ous matter,  but,  as  a  matter  of  fact,  taken  by  itself  it  gives 
little  information  of  value.     While  its  absence  is  conclusive, 


64  AIR,    WATER,    AND    FOOD. 

its  presence  is  not  equally  so;  but  a  proof  of  its  variability 
from  day  to  day  is  really  valuable.  Whether  used  in  the  final 
interpretation  or  not,  "  organic  nitrogen  "  (or  that  portion 
of  it  appearing  as  albuminoid  ammonia)  is  always  deter- 
mined, together  with  the  other  forms,  as  soon  as  the  sample  is 
received. 

A  nitrogenous  organic  compound  is  dangerous  from  one 
of  two  causes:  first,  because  it  is  already  decaying  and  har- 
bors pathogenic  germs  or  is  giving  off  toxines;  or,  second, 
because  it  will  furnish  food  for  a  further  development  of  bac- 
terial life. 

As  to  its  derivation  from  animal  or  from  vegetable  mat- 
ter, there  need  be  little  discussion,  especially  since  the  recog- 
nition of  the  high  nitrogenous  content  of  the  blue-green 
alga}  and  the  nitrogenous  character  of  "  soil-humus  "  and 
the  close  approximation  of  animal  and  vegetable  protoplasm 
But  it  is  most  important  to  know  if  it  is  stable,  since  one  of 
the  best  aphorisms  ever  contributed  to  the  literature  of  water- 
analysis  is  given  by  Dr.  Drown's  statement,  **  A  state  of 
change  is  a  state  of  danger." 

Results  of  the  Decay  of  Nitrogenous  Organic  Matter. — The 
products  of  the  first  stage  of  decay  of  this  class  of  organic 
matter  are  carbon  dioxide  and  ammonia.  It  is  to  the 
latter  that  we  turn  for  the  proofs  sought,  by  reason  of  the 
methods  at  hand  for  detecting  such  small  amounts  as  one 
part  in  a  billion  parts  of  water,  and  because  it  is  for  the  nitro- 
gen compound  that  we  seek. 

The  mere  presence  of  free  ammonia  is  not  a  sufficient  in- 
dication of  recent  pollution  from  human  sources.  Rain-water, 
as  shown  in  Table  III.  contains  considerable  quantities; 
decaying  blue-green  alg^e  furnish  it  in  still  larger  amounts, 
and  moreover  it  offers  acceptable  food  to  plant-life  and  may 
therefore    disappear    in    the    form    of    combined    nitrogen. 


water:    the  problem  of  safe  water.  65 

Nevertheless,  it  is  to  be  held  as  one  of  the  chief  witnesses,  for 
it  is  found  in  sewage  in  a  thousand  times  the  quantity  in 
which  it  occurs  in  ordinary  potable  water.  While  pULrefac- 
tive  decay  takes  place  by  stages,  the  lines  of  division  are  not 
sharply  drawn,  and  nitrites,  the  result  of  the  second  stage,  may 
be  and  usually  are  found  in  polluted  waters  together  with 
ammonia.  So  frequently  is  this  the  case  that  it  is  considered 
circumstantial  evidence  sufificient  to  convict  when  both  am- 
monia and  nitrites  are  found  together.  (See  Tables  V  and 
VI,  p.  199.) 

The  reason  is  not  far  to  seek.  Both  are  not  only  prod- 
ucts of  decay,  but  both  are  in  that  unstable  condition  which 
indicates  active  processes,  and  which  therefore  means  the 
presence  of  micro-organisms.  Certain  exceptions  will  be 
noted  later. 

The  fourth  form  of  nitrogen,  that  found  in  nitrates,  is  no 
longer  classed  as  organic;  it  is  now  become  food  for  green 
plants  and  cannot  nourish  the  class  to  which  bacteria  and 
pathogenic  germs  belong,  hence  it  is  fair  to  presume  that  for 
lack  of  food  the  latter  have  succumbed  or  have  been  other- 
wise removed.  The  value  of  this  test  is  the  proof  it  soinctimcs 
furnishes  of  previous  sewage  pollution,  since  the  nitrogen 
present  in  excess  of  that  brou-ght  down  by  rain  must  have 
been  furnished  either  by  fertilizers,  by  decaying  matter,  or  by 
sewage.    (See  Tables  V  and  VI,  p.  199.) 

Organic  Carbon. — Since  by  far  the  largest  constituent  of 
organic  matter  is  carbon,  some  fifty  per  cent.,  it  might  seem 
as  if  this  was  the  best  indication  of  pollution.  Indeed,  it  was 
formerly  so  considered,  and  many  methods  have  been  de- 
vised to  show  its  presence  quantitatively.  As  our  knowledge 
of  the  slight  differences  between  many  forms  of  animal  and 
vegetable  substances  grows,  the  probability  of  any  conclusive 
evidence  from  this  source,  either  as  to  past  history  or  prescn' 


66  AIR,    \VATER,    AND    FOOD. 

condition,  decreases.  In  short,  althou£?h  for  many  years 
water-analysts  have  been  striving  to  perfect  methods  of  de- 
tecting certain  sul^stances  and  certain  organisms,  it  would 
seem  as  if  they  were  no  nearer  a  discovery  of  one  simple  de- 
cisive test,  but,  in  most  cases,  were  driven  to  a  somewhat 
elaborate  examination  in  which  one  test  only  furnishes  one 
link  in  tlic  chain  of  evidence. 

Sauitarv  Analysis. — The  examination  of  a  water  to  deter- 
mine its  safety  for  domestic  use  is  called  a  sanitary  analysis, 
in  distinction  from  that  examination  which  determines  its 
fitness  for  manufacturing  purposes,  for  use  in  steam-boilers, 
or  its  medicinal  value. 

Four  points  are  to  be  determined:  First,  the  amount,  if 
any,  of  organic  matter  in  a  living  or  dead  condition,  sus- 
pended or  dissolved  in  the  water;  second,  the  amount  and 
character  of  the  products  of  decomposition  of  organic  mat- 
ter, and  their  relative  proportions  to  one  another;  third,  the 
stability  of  the  undecomposed  organic  substances;  fourth, 
the  amount  of  certain  mineral  substances  dissolved.  From 
these  results  we  draw  conclusions  as  to  the  present  condition 
and  past  history  of  the  water.  These  conclusions  are  not  in- 
fallible, but  there  are  enough  unavoidable  risks  in  human 
life  without  taking  unnecessary  ones;  and  if  pollution  is 
proved,  the  cause  should  be  removed  or  the  supply  aban- 
doned. 

Preliminary  Inspection. — So  long  as  the  eye  can  re-enforce 
the  other  tests  and  the  whole  course  of  the  water  may  be 
clearly  traced,  it  is  comparatively  easy  to  judge  of  the  charac- 
ter of  a  supply  and  of  its  safety  for  human  use;  but  when  a 
hole  in  the  ground  is  the  visible  source,  or  the  actual  history 
of  the  water  is  hidden  in  unknown  distances  and  depths,  the 
diagnosis  is  more  difificult. 

First,  the  geological  horizon  and  superficial  soil  must  be 


WATER  :     THE    PROBLEM    OF    SAFE    WATER.  6/ 

Studied;  the  direction  and  flow  of  underground  water,  not  ihe 
slope  of  the  surface  only;  the  possible  sources  of  danger, 
occasional  as  well  as  constant,  within  at  least  a  quarter  of  a 
mile  radius.  The  composition  of  unpolluted  water  of  the 
same  region  should  always  be  at  hand  for  consultation. 

Safe  Wafer. — As  has  been  said,  we  can  no  longer  require 
pure  water;  the  most  that  we  can  demand  is  that  the  supply- 
shall  be  safe.  To  the  uninitiated  one  sample  of  clear,  color- 
less water  seems  very  like  any  other.  The  safe,  colored  or 
muddy  water  of  a  stream  or  pond  seems  less  desirable  than 
the  clear,  cold  water  of  a  badly  polluted  well. 

A  water  may  be  normally  safe  and  yet,  from  exceptional 
circumstances,  be  for  a  time  a  source  of  danger.  In  one  case 
the  mouth  of  a  well  at  a  factory  was  overflowed  l)y  a  con- 
taminated brook  raised  above  its  usual  level  by  a  heavy 
shower  for  half  an  hour  only.  Some  thirty  cases  of  typhoid 
fever  resulted,  so  close  to  one  another  and  so  suddenly  ceas- 
ing as  to  leave  no  doubt  of  the  fact  that  for  only  a  few  hours 
was  the  water  unsafe.  How,  then,  shall  a  chemist  tell  if  at 
some  past  time  a  water  may  have  been  or  at  some  future  time 
may  become  a  source  of  disease?  Only  by  carefully  weigh- 
ing all  the  testimony  attainable — ocular,  chemical,  biological, 
bacteriological — in  the  light  of  past  experience. 

The  day  of  the  vest-pocket  sample,  usually  in  a  flavoring- 
extract  bottle,  cork  and  all,  is  nearly  past,  but  that  of  the 
fruit-jar,  with  a  sticky  rubber  ring  and  corroded  zinc  top,  is 
still  with  us.  That  admiration  for  chemical  knowledge  and 
belief  in  chemical  clairvoyance  which  expects  the  chemist  to 
decide  from  a  sample  while  you  wait  if  a  certain  water  caused 
the  death  of  a  person  a  month  since  in  a  distant  town  under 
unknown  conditions  is  very  trying  to  the  man  who  knows  his 
own  limitations. 

The  market  value  of  an  analysis  cannot  well  be  appre- 


68  AIR,    WATER,    AND    FOOD. 

ciated  until  a  juster  estimate  of  the  professional  training  of 
the  analyst  is  a  part  of  common  knowledge. 

Safe  and  Acceptable  Water. — It  is  not  enough  that  a 
supply  shall  be  free  to-day  from  disease-germs;  it  should  re- 
main free  from  changes  for  a  reasonable  period  of  time. 
Therefore  the  advice  desired  by  the  towns  seeking  for  sup- 
plies implies  much  more  than  mere  analysis;  it  includes  esti- 
mates of  future  changes,  of  variations  due  to  possible  further 
developments,  and  of  the  effect  of  these  variations  on  accept- 
ability as  well  as  safety. 

To  be  fully  acceptable,  a  water  should  be  free  from  color, 
odor,  turbidity,  sediment,  and  of  a  uniform  temperature  so 
low  as  to  admit  of  use  without  ice.  Only  such  water  as  has 
been  earth-filtered  and  earth-cooled  can  meet  this  demand, 
but  the  supply  of  this  class  is  becoming  drawn  upon  to  its 
limit;  besides  there  are  difficulties  in  the  conveyance  and 
storage  of  ground-water  which  offset  many  of  its  advantages. 

From  the  foregoing  paragraphs  it  will  be  seen  not  only 
that  waters  carry  every  possible  degree  of  safety  or  danger 
according  to  the  country  they  drain,  the  num'ber  and  habits 
of  the  people  living  on  the  watershed,  and  the  presence  or 
absence  of  factories,  slaughter-houses,  etc.,  but  that  many 
elements  enter  into  the  judgment  of  a  water-supply,  and  how 
dhiferent  these  elements  are  in  different  waters.  Safe  water 
is  that  which  carries  neither  seeds  of  disease  nor  such  sub- 
stances as  are  deleterious  in  any  way  to  mankind  in  general. 

A  brown  water  may  yield  20  parts  per  million  organic 
matter  and  show  10  parts  oxygen  consumed,  and  yet  be  a 
safe  and  wholesome  water.  A  ground-water  may  show  5 
parts  nitrates,  and  yet  for  ten  or  twenty  years  prove  a  safe 

supply. 

Since,  however,  water  is  so  universally  made  a  carrier  of 
refuse,  it  is  difficult  to  find  a  stream  or  well  which  fulfils  the 


^YATER:     THE   TROBLEM    OF   SAFE   WATER.  69 

above  exacting  requirements,  and  a  compromise  is  made 
which  sets  certain  arbitrary  limits  and  so  keeps  the  chances 
small.  Such  limits  are  very  misleading  of  themselves,  espe- 
cially if  used  over  a  wide  extent  of  territory.  The  English 
standards,  for  instance,  are  not  applicable  to  eastern  North 
America.  Only  a  study  of  all  local  conditions  and  a  wise  in- 
terpretation of  all  results  can  make  standard  figures  of  any 
significance.  This  is  true,  also,  of  bacterial  results  in  surface- 
waters.  In  the  natural  condition  of  lakes  and  streams  there 
are  so  many  varieties  of  bacteria  present  and  in  such  varying 
numbers,  according  to  wind  and  rain  and  watershed,  that 
taken  alone  the  numerical  count  gives  no  more  convincing 
proof  than  is  found  in  chemical  figures. 

While  it  is  quite  within  the  limits  of  possibility  that  a 
culture-tube  of  typhoid  bacilli  might  be  emptied  into  the 
middle  of  a  river  or  be  washed  into  a  reservoir,  and  chemical 
analysis  give  no  sign,  yet  no  continuous  natural  means  of 
contamination  is  known  which  is  not  accompanied  by  sub- 
stances readily  detected  by  suitable  chemical  examination. 
In  either  case  an  epidemic  may  or  may  not  result,  dependent 
upon  causes  other  than  the  mere  presence  or  absence  of  the 
micro-organisms. 

If  drainage  from  a  house  or  barn  is  seen  entering  a 
stream,  it  does  not  need  a  dozen  plate-cultures  to  prove  that 
there  is  possible  danger.  Such  tests  may,  however,  when 
used  with  skill,  serve  to  trace  contamination  back  to  iis 
source,  and  is  another  means  at  the  service  of  the  trained 
water-works  superintendent  whereby  he  can  keep  a  close 
watch  over  the  character  of  his  supply. 

As  a  means  of  control  of  the  efficiency  of  filter-plants  the 
bacterial  examination  is  invaluable,  and  as  a  knowledge  of 
the  forms  which  accompany  pathogenic  germs  becomes  more 
certain   tlie   value   of  these   tests  will    increase,   even   if  tlie 


70  AIR,    WATER,    AND    FOOD. 

classification  and  identification  is  not  perfected  to  scientific 
accuracy. 

It  is  one  of  the  penalties  of  living  in  a  large  city  that  the 
water-supjily  must  of  necessity  be  surface-water  which  has 
been  caught  and  stored  at  a  distance  or  that  whicli  has  been 
filched  from  a  stream,  filtered  and  made  passable.  Conse- 
quently education  must  take  the  place  of  instinct,  and  custom 
must  make  that  acceptable  which  circumstances  render 
necessary. 

THE  INTERPRETATION  OF  ANALYSES. 

Experience  in  cutting  through  glacial  moraines  for  rail- 
ways or  in  driving  levels  for  mining  operations  does  not 
qualify  a  man  for  exploration  of  a  Babylonian  or  prehistoric 
mound.  Human  occupations  have  left  upon  the  sand  and 
clay  evidences  which,  although  so  slight  as  to  be  unnoticed 
by  the  casual  observer,  are  like  an  open  book  to  him  who 
patiently  acquires  a  knowledge  of  the  meaning  of  the  dis- 
placements, discolorations,  and  enclosed  fragments.  Flowing 
water,  like  sand  and  clay  strata,  bears  evidences  of  its  previous 
history  no  less  intelligible  to  him  who  has  the  key  to  the 
cipher  and  who  adds  to  the  keen  eye  of  the  detective  and 
ready  wit  of  the  interpreter  the  sound  judgment  of  the  engi- 
neer. Reasoning  upon  insufficient  premises  will  as  often 
fail  in  the  one  case  as  in  the  other,  while  lucky  guesses  fre- 
quently encourage  superficiality  in  both. 

After  the  analyst  has  entered  on  the  blank  (page  120)  the 
six  to  ten  records  needed  for  a  ground-water,  or  the  fifteen 
to  twenty  for  a  surface-water:  after  the  columns  headed 
Bacteria,  Diatoms,  Algae,  etc.,  have  been  filled  in,  there  still 
remains  the  summing  up  of  the  case  by  the  judge.  The 
correct  interpretation  of  results  means  a  knowledge  of 
the    source,     geological     horizon,     surroundings,     probable 


water:    the  interpretation  of  analyses.        71 

changes,  and  the  significance  of  each  item  in  this  particular 
case.  Each  class  of  water  has  its  own  characteristics.  The 
presence,  in  quantity,  of  any  given  element  is  interpreted 
according  to  the  kind  of  water  under  consideration.  Spring- 
water  is,  of  course,  colorless;  lake-water  of  equal  safety  is 
probably  colored.  Spring-water  must  be,  as  a  rule,  free  from 
ammonia;  lake-water  may  at  times  contain  considerable 
amounts  without  detracting  from  its  good  character. 

Classification  of  Waters.  —  To  facilitate  examination, 
therefore,  waters  may  be  divided  into  three  classes:  first, 
cistern,  brook,  pond,  and  river  water — so-called  surface- 
zvatcr;  second,  spring  and  deep-well  water;  and  third,  shal- 
low wells  and  sewage  effluents. 

Water  of  the  last  two  classes  has  been  for  greater  or  less 
periods  of  time  in  contact  with  rock  and  filtered  through 
sand,  hence  is  designated  as  ground-zvater. 

A  few  examples  taken  from  the  difTerent  kinds  of  water 
showing  the  varying  conditions  to  which  they  are  subjected 
may  serve  to  make  the  rules  of  interpretation  clearer. 

Surface-Waters. — When  rain-water  falls  on  slated  or 
shingled  roofs  and  is  conducted  into  cisterns,  it  carries  wi:h 
it  whatever  deposits  lave  collected,  the  pollen  of  forest-trees 
or  disease-germs  from  city  slums  many  miles  away;  from 
metal  roofs  it  takes  either  the  metal  itself  or  the  paint  used 
to  protect  the  surface.  In  all  cases,  lower  forms  of  animal 
life,  small  insects,  and  soot  from  chimneys  may  be  present. 
These  foreign  substances  should  be  at  once  filtered  out  with- 
out allowing  time  for  organic  decay,  unless  there  is  an  auto- 
matic device  for  wasting  the  first  washings  of  the  collecting 
surface.  There  are  still  substances  in  solution  whicli  would 
be  better  away;  therefore  the  water  is  allowed  to  stand 
quietly  in  order  that  the  changes  may  have  time  to  take 
place — to  ferment,  as  it  is  often  technically  expressed.     After 


72  AIR,    WATER,    AND    FOOD. 

this  season  of  purification  the  water  is  again  filtered  and 
stored  ready  for  use.  There  is  usually  color  and  a  little  am- 
monia, but  rarely  nitrates.  The  soluble  metals,  if  once  pres- 
ent, still  remain.  It  goes  without  saying  that  all  such 
cisterns  must  be  absolutely  impervious  to  surface  drainage. 
For  lack  of  one  or  all  of  these  precautions,  cistern-water  has 
often  been  found  to  be  contaminated  from  cesspools,  from 
leaden  or  painted  roofs,  or  from  decaying  organic  matter. 

Brook-zvatcr. — The  rain  that  falls  on  mountain  slopes  of 
granitic  or  other  insoluble  rocks  washes  from  them  whatever 
loose  earth  may  have  fallen  there,  and  from  the  firmly  fixed 
lichens  the  small  insects  and  other  animal  forms  which  they 
harbor.  These  are  transported  in  brooks  to  the  lower  lands 
where  the  organisms  decay,  the  heavier  earthy  particles  fall- 
ing out  by  the  way. 

If  the  upland  rocks  and  soil  yield  a  portion  of  mineral 
salts  to  the  water,  it  may  come  out  clear  and  colorless  even  if 
it  has  not  penetrated  to  an  appreciable  depth. 

The  water  from  these  forest  brooks,  after  remaining  im- 
pounded in  a  clean  lake  or  reservoir,  exposed  to  sunlight  and 
air,  often  becomes  the  safest  source  of  supply.  As  with  cis- 
terns, so  with  reservoirs,  filtration,  natural  or  artificial,  may 
take  place  previous  or  subsequent  to  storage,  or  both  before 
and  after. 

Lake  or  Mixed  Water. — Lakes  are  fed  by  springs  as  well 
as  by  brooks,  or  by  that  portion  of  rainfall  which  passes  a  few 
inches  below  the  surface,  and  is  filtered  before  reaching  the 
main  body.  If  the  banks  are  sandy  and  uninhabited,  the 
water  will  show  good  effects  from  this  filtration;  but  if  the 
seepage-water  comes  from  a  settled  country,  it  will  bring 
either  ammonia  or  nitrates.  The  analysis  will  quickly  show 
this  if  the  water  sample  can  be  taken  before  it  has  mixed 
with   that   bearing  the   spores   of  plants   which   are   fed   by 


water:   the  interpretation  of  analyses.       73 

nitrates.     Often  the  very  presence  of  these  plants  furnishes 
the  proof  sought. 

Rk'cr-zvatcrs. — A  large  stream,  like  the  Mississippi,  may- 
receive  the  drainage  of  half  a  dozen  cities  a  hundred  miles 

distant  and  yet  not  give  conclusive  evidence  of  dangerous 
contamination,  while  a  small  river,  like  the  Potomac,  may 

become  unsafe  from  the  presence  of  a  few  villages  a  dozen 

miles  away. 

Northeastern  America  is  so  well  supplied  with  uninhab- 
ited high  lands  for  collecting-grounds,  and  with  basins  in  the 
glacial  drift  for  storage  in  natural  or  artificial  lakes,  that  very 
few  rivers  need  to  be  used  after  they  have  become  polluted. 
The  Merrimac  and  the  Hudson  are,  however,  so  used.  In 
other  parts  of  the  country  the  use  of  rivers  is  an  increasing 
necessity. 

From  every  point  of  view  organic  matter  should  be  kept 
as  far  as  possible  out  of  running  streams  which  may  at  any 
time  be  needed  for  public  supplies,  or  the  natural  purifica- 
tion by  algae  should  precede  the  final  filtration  and  storage. 
It  is  quite  probable  that  this  double  treatment  may  be  more 
frequently  required  as  unpolluted  water  becomes  more 
scarce. 

What  the  method  of  filtration  shall  be  depends  upon  the 
character  of  the  water,  whether  clear  or  turbid  with  clay, 
whether  certainly  polluted  or  only  with  a  remote  possibility 
of  contamination.  Each  problem  must  be  studied  by  itself 
without  prejudice  in  favor  of  any  one  method.  It  is  the  re- 
sult which  must  be  kept  in  mind,  namely,  the  furnishing  of 
safe  and  acceptable  water  to  the  community. 

Effect  of  the  Storage  of  Surface-water. — In  interpreting 
his  results,  the  analyst  should  take  into  account  the  influence 
which  the  keeping  of  water  in  basins  has  upon  its  character. 
Storage  of  surface-water  is  of  utmost  importance  in  all  cases 


74  AIR,    WATER,    AND    FOOD. 

of  doubt.  Most  disease-germs  find  such  water  an  unfavor- 
able medium  for  prolonged  life,  since  exposure  to  sunlight 
soon  destroys  the  darkness-loving  bacteria,  and  a  certain 
sterilizing  etTect  results  from  the  growth  of  green  algie,  so 
that  water  considerably  polluted  becomes  purified  if  given 
time  for  the  various  agents  to  do  their  work;  but  time  is 
essential. 

Odors. — For  surface-waters  one  of  the  links  in  the  chain 
of  evidence  is  found  in  the  odor,  cold  and  hot.  which  to  the 
trained  and  sensitive  nose  often  gives  convincing  testimony. 
A  musty  odor,  unmistakably  different  from  a  mouldy  vege- 
table smell,  betrays  sewage  contamination  even  when  the 
chemical  analysis  might  not  be  convincing.  This  odor  is  not 
always  taken  out  by  filtration,  neither  is  that  of  certain  or- 
ganisms growing  in  stored  water,  notably  Anabccna  and 
Syiiura.  A  study  of  these  organisms  is  invaluable  to  the 
routine  observer  who  watches  the  seasonal  and  annual 
changes  in  his  reservoir, 

Turbidifx  and  Sediment. — The  determination  of  turbid- 
ity and  sediment,  added  to  the  odor,  tells  much  to  the  expert, 
but  very  little  to  the  inexperienced  student.  Turbidity  may 
be  due  to  drainage  contamination,  to  growth  of  bacteria,  to 
clay,  to  iron,  to  swarms  of  micro-organisms.  Sediment  may 
be  sand,  zooglea,  fragments  of  plants  or  animals,  or  ferric 

oxide. 

Filtration. — The  subject  of  filtration  has  been  so  exten- 
sively treated  elsewhere  that  the  student  is  referred  to  the 
bibliography  on  page  213.  There  are  cases  in  which  it  is 
preferable  to  run  the  risk  of  too  much  alum  in  the  drinking- 
water,  and  too  much  sulphuric  acid  in  boiler  feed-w^ater, 
rather  than  of  too  many  micro-organisms  with  the  accom- 
panying organic  matter. 

It  will  have  been  noticed  that  the  ideal  natural  water  is 


water:    the  interpretation  of  analyses.        75 

that  which  has  been  earth-filtered,  and  thus  all  suspended 
matter,  including  microbes,  has  been  removed.  This  sup- 
poses that  sufficient  time  has  elapsed  so  that  all  decomposing 
organic  matter  has  been  destroyed.  Man  tries  to  imitate 
nature's  processes,  but  expects  to  accomplish  it  in  moments 
instead  of  months. 

The  era  of  house-filters,  those  admirable  culture-grounds 
for  bacteria,  is  happily  nearly  past.  Taxpayers  are  becoming 
convinced  that  a  good  original  water-supply  in  competent 
hands  is  worth  paying  for.  Where  straining  only  is  needed, 
a  flannel  bag  washed  daily  is  as  efficient  as  any  faucet-filter. 
If  the  latter  takes  out  color  as  well,  it  should  be  closely 
watched.  Water  should  not  be  first  boiled  and  then  filtered, 
but  first  filtered  and  then  boiled. 

^Sumniary. — Surface-ivatcr. — In  general  it  may  be  said 
that  the  waters  of  the  first  class  found  in  New  England  are 
generally  more  or  less  colored,  and  contain  more  or  less  sus- 
pended organic  life  and  its  debris,  which  often  impart  a  de- 
cided odor  to  the  water.  These  waters,  draining  for  the  most 
part  wooded  and  sparsely  populated  regions,  are  low  in  free 
ammonia,  nitrates,  and  nitrites;  low,  also,  in  mineral  salts, 
and  with  only  a  slight  excess  of  chlorine  over  the  normal. 
They  are  usually  high  in  organic  matter  and  albuminoid  am- 
monia even  when  entirely  free  from  pollution. 

In  other  parts  of  the  United  States  surface-waters  may  be 
low  in  color,  but  with  much  suspended  clay  and  silt,  and  may 
hold  in  sohition  notable  quantities  of  mineral  salts.  The 
latter  aid  greatly  in  the  clarification  by  artificial  filtration, 
which  is  so  often  rendered  necessary  by  the  excessive  turbid- 
ity even  if  not  by  sewage  contamination. 

'In  Table  IV,  page  198,  will  be  found  examples  showing 
at  a  glance  how  profoundly  the  character  of  a  water  is  affected 
by  the  geological  horizon,  whether  its  source  is  in  the  glacial 


76  AIR,    WATER,    AND    FOOD. 

drift  of  the  Appalachian  region,  or  in  the  Hmestone  of  the 
Hudson  River  Valley,  or  in  the  saline  deposits  of  the  sub- 
sided areas. 

Dccf^  ]VcUs  and  Springs. — The  waters  of  the  second  class 
are  derived  from  the  depths  of  the  earth,  far  below  any  pos- 
sible surface  contamination,  and  have  long-  been  imprisoned 
in  the  dark  and  cold,  and  often  subjected  to  great  pressure. 
The  influence  of  pressure  on  organisms  has  not  been  entirely 
worked  out,  but  from  what  is  known  it  is  probably  very  un- 
favorable to  the  life  of  the  lower  organisms.  The  results  of 
many  bacterial  examinations  have  been  vitiated  by  the  diffi- 
culty of  securing  a  sample  from  great  depths  without  con- 
tamination by  surface  exposure — pipes  open  to  the  air  har- 
boring many  forms  of  life. 

Deep  wells,  700  feet  and  more,  are  not  likely  to  be  dan- 
gerous. They  may  often  contain  ammonia  from  prehistoric 
coal-fields  or  tertiary  deposits,  but  rarely  nitrates.  This  is 
accounted  for  by  the  fact  that  "  the  result  of  the  changes  of 
the  nitrogenous  organic  substances  which  fall  into  the  earth 
is,  without  doubt,  frequently  the  formation  of  gaseous  nitro- 
gen." Also,  that  "  salts  of  nitric  acid  on  penetrating  into 
the  depths  of  the  earth  give  up  their  oxygen."  * 

Owing  to  their  long  sojourn  in  the  depths  of  the  earth, 
these  waters  are  higher  in  mineral  substances  than  surface- 
waters.  Since  their  origin  is  unknown,  the  chlorine  cannot 
be  correctly  gauged,  especially  as  there  are  saline  waters  deep 
down  in  rock  cavities  in  all  parts  of  the  world. 

It  is  usually  believed  that  these  deep  wells  furnish  a  safe, 
palatable  water  when  the  kind  and  amount  of  mineral  matter 
is  not  objectionable. 

Shallozv  Wells. — It  is  not  to  be  wondered  at  that  waters 

*  Mendeleeff:   "  Chemistry,"  p.  223. 


WATER:     THE    INTERPRETATION   OF    ANALYSES.  7/ 

of  the  third  class — ground-water,  taken  from  just  beneath 
the  surface  layers  of  the  soil — should  contain  many  sub- 
stances foreign  to  the  waters  about  them  as  well  as  to  those 
at  greater  depths.  The  shallow  wells,  which  are  practically 
more  or  less  diluted  sewage  effluents,  present  the  greatest 
variety.  They  may  be  clear  and  colorless  and  show  as  great 
organic  purity  as  the  best  mountain  spring.  In  other  cases, 
the  overworked  filter  permits  the  passage  of  organisms  and 
undecomposed  material.  In  either  case  there  will  be  found 
those  compounds  which,  being  soluble  and  stable,  are  car- 
ried with  the  water  as  signs  to  be  read  by  him  who  knows  the 
language,  A  complete  history  of  each  specimen  of  this  class 
of  ground-water  is  desirable,  and  with  sufflcient  patience 
and  care  it  may  be  obtained  with  reasonable  accuracy,  if  the 
principles  governing  the  circulation  of  water  and  the  changes 
of  the  organic  matter  it  carries  be  kept  well  in  mind. 

It  is  certain  at  once  that  absence  of  color,  of  organic  mat- 
ter in  any  form,  and  of  odor  should  be  insisted  upon,  for 
ground-water  is  filtered  w^ater  and  the  filter  should  be  doing 
its  work. 

A  modicum  of  geological  knowledge  is  essential,  as  the 
presence  of  shaly  or  slaty  rock  will  permit  the  passage  into 
underground  water  of  surface  drainage  with  less  purification 
than  will  a  granite  or  sandstone  region,  A  clayey  soil  is  a  less 
efficient  filter  than  a  sandy  loam  and  permits  the  pollution 
to  travel  farther. 

Nitrogen  in  Well-water — It  may  be  taken  as  an  axiom 
that  the  only  form  of  nitrogen  permissible  in  a  good  ground- 
water is  that  of  nitrates,  a  fully  oxidized  or  mineralized  food 
for  green  plants.  If  nitrites  are  also  present,  a  source  of 
pollution  is  at  hand,  for,  as  has  been  said,  nitrites  indicate 
either  a  stage  of  oxidation  not  completed  or  one  of  reduction 
from  nitrates  in  the  presence  of  organic  matter.     If  free  am- 


78  AIR,    WATER,    AND   FOOD. 

monia  be  present,  it  is  safe  to  say  that  the  source  is  not  only 
near  but  in  actual  contact,  since  but  a  few  hours'  time  is 
needed  to  oxidize  the  ammonia  in  any  soil  not  waterlogged. 
It  may  also  be  pretty  safe  to  assume  that  bacteria  are  present, 
since  ammonia  is  the  first  stage  of  that  decomposition  which 
they  accompany.  It  is  the  part  of  prudence,  therefore,  to 
avoid  any  water  which  contains  both  free  ammonia  and 
nitrites  above  .200  or  .300  parts  per  million  of  the  first,  and 
.020  or  .030  of  the  second. 

The  absorption  of  nitrogen  by  plants  is  rarely  complete, 
so  that  it  usually  appears  in  far  larger  quantities  in  contami- 
nated ground-waters  than  could  be  obtained  from  purified 
rain-water.  The  leaching  cesspool  discharges  its  liquid  con- 
tents below  the  zone  of  green-plant  life;  fertilized  soil  also 
yields  a  portion  of  its  food  value  to  the  lower  layers.  A 
small  portion  of  the  nitrogen  of  vegetable  origin  may  appear 
as  nitrates,  but  only  as  a  derivative  of  soil  rich  in  humus  is  it 
likely  to  play  any  considerable  part.  In  eastern  America 
nitrates  above  0.5  parts  per  million  would  arouse  suspicion, 
and  above  5  parts  would  in  most  cases  prove  previous  pollu- 
tion. 

It  is  evident  that  in  the  use  of  nitrogen  as  an  indicator  of 
the  conditions  of  a  water  we  are  limited,  by  the  changeful 
character  of  the  compounds,  to  certain  not-to-be-mistaken 
amounts,  and  that  in  the  majority  of  cases  the  evidence  given 
is  not  decisive. 

Chlorine  hi  Well-zvater. — Fortunately  there  is  another  ele- 
ment not  so  eagerly  sought  for  by  plants  and  not  liable  to  so 
many  transformations.  Thanks  to  the  great  solubility  of  its 
common  compounds  and  to  their  stability,  chlorine,  once  a 
constituent  of  a  given  body  of  water,  is  not  extracted  there- 
from and  remains  as  a  telltale  to  reveal  the  past  history  of  a 
stream  or  spring.     If  a  man  is  judged  by  the  company  he 


water:   the  interpretation  of  analyses.        79 

keeps,  much  more  a  water-supply.     From  sewage  all  the 
nitrogen  may  be  removed  and  the  chlorine  still  remain. 

But  in  order  to  use  this  information  with  any  degree  of 
certainty  the  normal  chlorine  of  the  locality  must  be  known. 
If  a  map  showing  isochlors  has  been  made  of  the  region  or 
State,  and  if  there  are  no  geological  deposits  to  interfere,  this 
is  easy;  but  if  the  chemist  or  engineer  has  an  unknown  coun- 
try to  report  upon,  it  will  be  necessary  to  examine  the  local 
conditions  and  to  choose  six,  eight,  or  ten  samples  of  prob- 
able freedom  from  contamination  and  to  test  them  for  com- 
parison. The  sources  of  the  excess  of  chlorine  over  the 
normal  are  usually  the  sink-drain  with  its  burden  of  salted 
water  from  domestic  operations;  the  house-drain,  with  its 
chlorine-containing  excreta;  and  the  stable-drain,  with  a 
slight  chlorine  content  in  comparison  with  the  other  two. 

Mineral  Substances. — Since  water  Is  a  universal  solvent, 
it  is  not  surprising  to  find  considerable  amounts  of  mineral 
matter  in  the  two  columns  "  Total  Solid  Residue  on  Evapo- 
ration "  and  "  Hardness."  How  much  calcium  sulphate  or 
magnesium  chloride  or  other  soluble  mineral  is  allowable  in 
a  potable  water  is  for  the  physician  rather  than  the  chemist 
to  say.  As  has  been  said,  the  human  system  possesses  great 
adaptability,  not  only  for  different  foods,  but  for  mineral  sub- 
stances water-carried.  Not  so  the  steam-boiler  or  the  laundry- 
tub,  which  reacts  very  sensitively  and  affects  the  pockets 
of  the  consumers.  In  a  region  of  soft  water,  high  solids 
with  chlorine  and  nitrates  indicate  sewage  pollution. 
Silica  is  much  more  commonly  present  even  in  surface- 
waters  than  is  often  supposed.  What  its  effect  may  be  is 
unknown.  Iron  is  not  uncommonly  found  in  combination 
with  organic  matter  in  either  surface  or  imperfectly  filtered 
waters  in  contact  with  soils  poor  in  calcium  salts.  It  is  fre- 
quently accompanied   by   free   ammonia,   which    causes   an 


So  AIR,    WATER,    AND    FOOD. 

abiiiulant  growth  of  Crcnothrix.  It  is  also  present  in  deep 
wells  in  the  form  of  carbonate,  which  precipitates  on  exposure 
to  warm  air. 

In  a  considerable  number  of  cases  of  public  water-supply 
there  is  a  mixture  of  surface  and  ground  water  which  com- 
plicates the  verdict,  requiring  a  most  delicate  l)alancing  of 
probabilities.  The  mineral  contents  often  aid  in  this  deci- 
sion. Well-waters,  too,-  are  often  exposed  to  surface-wash 
because  of  poor  protection  at  the  mouth.  Cyclops  or  other 
surface-water  organisms  often  indicate  this. 

Water-pipes. — After  all,  if  the  pipes  conveying  the  water 
are  of  lead  or  brass,  an  additional  danger  appears.  Gen- 
erally speaking,  the  purer  the  water  the  greater  the  risk. 
No  common  metal  seems  to  withstand  the  action  of  soft 
water;  six  to  eight  years  being  the  average  age  of  galvanized 
pipe,  and  eight  to  ten  of  iron  pipe.  It  would  seem  as  if 
cement-lined  pipe  must  come  into  greater  use  until  some 
kind  of  glass  is  invented  which  will  withstand  this  corrosive 
action  and  yet  admit  of  plumber's  connections. 

Value  of  Tests. — It  is  often  asked  if  some  tests  cannot  be 
made  by  the  ordinary  person  of  average  intelligence  which 
will  enable  him  to  tell  the  quality  of  a  water  as  well  as  the 
expert  to  whom  he  pays  ten  or  twenty  dollars  for  an  opinion. 
A  careful  perusal  of  the  preceding-  pages  will  have  answered 
the  question  in  the  negative.  There  is  no  assay  of  water  as 
there  is  of  gold  and  silver.  Not  one  but  ten  or  twenty  tests 
must  be  made.  Not  only  must  the  tests  be  made  with  the 
utmost  care  and  cleanliness  of  person,  utensils,  and  room,  but 
the  results  must  be  studied  in  the  light  of  other  experience 
and  other  knowledge,  geological  and  biological,  and  after 
all  this  is  done  there  is  an  array  of  circumstantial  evidence 
which  must  be  carefully  weighed  by  one  whose  judgment  and 
experience  enable  him  to  read  clearly  where  another  might 


water:    the  interpretation  of  analyses.        8 1 

see  nothing.  The  value  of  a  water-analysis  is  in  direct  pro- 
portion to  the  knowledge  and  experience  of  the  one  who 
interprets  it.  Clinical  skill  in  addition  to  theoretical  knowl- 
edge is  required  to  interpret  the  figures  obtained  in  the  course 
of  a  water-analysis,  as  in  the  symptoms  of  a  disease:  and  the 
analogy  goes  still  further,  for  as  some  diseases  are  clearly 
defined,  others  are  so  complicated  that  only  those  who  have 
had  long  experience  can  outline  a  safe  course  of  treatment; 
so  some  waters  bear  the  marks  of  their  character  so  plainly 
as  not  to  admit  of  mistake,  while  others  require  most  careful 
study.  For  these  reasons  the  value  of  water-analysis  should 
not  be  decried  because  the  fears  aroused  by  reports  given  by 
unskilled  analysts  prove  groundless,  any  more  than  the  prac- 
tice of  medicine  should  be  discarded  because  inexperienced 
men  make  mistakes. 

Is  the  water  in  any  given  case  safe  for  drinking?  To  an- 
swer this  question  there  is  needed  a  knowledge  wider  than  a 
chemist's  of  the  relation  of  decaying  organic  matter  and  of 
the  germ-carrying  power  of  water  to  outbreaks  of  disease. 
There  must  be  added  the  knowledge  of  the  biologist,  the  en- 
gineer, and  the  sanitarian. 


CHAPTER  VIL 


ANALYTICAL    METHODS. 


General  Statements. — Water-analysis  cannot  be  carried  orr 
in  an  ordinary  laboratory.  In  order  to  obtain  satisfactory 
results  it  is  necessary  to  have  a  room  set  apart  for  the  pur- 
pose, and  to  exclude  rigidly  all  operations  which  tend  to  the 
production  of  fumes  or  dust.  Where  such  minute  traces  of 
substances  are  dealt  with  as  in  water-analysis,  too  much  care 
cannot  be  taken  to  insure  the  absolute  cleanliness  of  the  ap 
paratus  and  the  surroundings.  It  is  desirable  that  the  room 
be  well  Hghted,  and  if  possible  the  windows  should  face 
toward  the  north. 

The  methods  for  the  examination  of  W'ater  which  are  de- 
scribed in  this  chapter  by  no  means  comprise  all  that  are  in 
use.  The  directions  are  given  for  the  use  of  students  in  our 
own  laboratory  under  the  conditions  obtaining,  i.e.,  of  large 
classes  and  of  several  courses  of  study,  with  especial  reference 
to  educational  rather  than  purely  technical  needs,  and  in  some 
cases,  no  doubt,  the  traditions  of  thirty  years  may  have  unduly 
persisted.  The  methods  have  been  so  selected  as  to  intro- 
duce a  variety  of  apparatus  and  to  illustrate  principles.  They 
have  also  been  subjected  to  a  thorough  test  in  meeting  the 
demands  of  practical  work. 

Colleetion  of  Samples. — For  the  collection  of  w^ater  sam- 
ples, glass-stoppered  bottles  of  about  a  gallon  capacity  are 
best.     Those  used  in  this  laboratory  are  of  white  glass,  fifteen 

inches  high  to  the  top  of  the  stopper,  five  and  a  half  inches 

82 


water:  analytical  methods.  83 

in  diameter,  and  weigh  about  three  pounds.  They  have  flat, 
mushroom  stoppers,  on  which  is  engraved  a  number  to  corre- 
spond with  that  on  the  bottle.  The  bottles,  before  being 
sent  out,  are  thoroughly  cleaned  with  potassium  bichromate 
and  sulphuric  acid,  washed  with  distilled  water  and  dried.  If 
glass-stoppered  bottles  are  not  at  hand,  new  demijohns  fitted 
with  iiczv  corks  may  be  used.  A  glass  bottle  or  a  demijohn 
is  much  to  be  preferred  to  an  earthenware  jug,  because,  if  for 
no  other  reason,  it  is  so  much  easier  to  be  sure  that  the  interior 
is  clean.  It  should  always  be  borne  in  mind  that  in  water- 
analysis  the  question  is  one  of  very  minute  quantities  of  mate- 
rial, and  that  the  methods  to  be  employed  are  extremely 
delicate.  Hence,  in  the  case  of  many  waters,  careless  hand- 
ling of  the  sample  would  contaminate  the  water  to  a  sufftcient 
extent  to  render  valueless  the  results  obtained  in  the  labora- 
tory. In  collecting  samples,  the  following  directions  should 
be  closely  followed:  * 

Directions  for  Collecting  Samples  for  Analysis — From 
a  Water-tap. — Let  the  water  run  freely  from  the  tap  for  a 
few  minutes  'before  collecting  the  sample.  Then  place  the 
bottle  directly  under  the  tap  and  rinse  it  out  with  the  water 
three  times,  pouring  out  the  water  completely  each  time. 
Place  it  again  under  the  tap;  fill  it  to  overflowing  and  pour 
out  a  small  quantity  so  that  there  shall  be  left  an  air-space 
under  the  stopper  of  about  an  inch.  Rinse  off  the  stopper 
with  flowing  water;  put  it  into  the  bottle  while  still  wet  and 
secure  it  by  tying  over  it  a  clean  piece  of  cotton  cloth.  Seal 
the  ends  of  the  string  on  the  top  of  the  stopper.  Under  no 
circumstances  touch  the  inside  of  the  neck  of  the  bottle  or 
the  stem  of  the  stopper  with  the  hand,  or  wipe  it  with  a 
cloth. 

From  a  Stream,  Pond,  or  Reservoir. — Rinse  the  bottle  and 

*  Ann.  Rep.  Mass.  State  Board  of  Health,  1890,  p.  520. 


84  AIR,    WATER,    AND    FOOD. 

Stopper  with  the  water,  if  tliis  can  be  done  without  stirring 
up  the  sediment  on  the  bottom.  Then  sink  the  bottle,  with 
the  stopper  in  place,  entirely  beneath  the  surface  of  the  water 
and  take  out  the  stopper  at  a  distance  of  twelve  inches  or 
more  below  the  surface.  When  the  bottle  is  full  replace  the 
stopper,  below  the  surface  if  possible,  and  secure  it  as  directed 
above.  It  will  be  found  convenient,  in  taking  samples  in 
this  way,  to  have  the  bottle  weighted  so  that  it  will  sink  be- 
low the  surface,  and  to  remove  the  stopper  by  a  cord.  It  is 
important  that  the  sample  should  be  obtained  free  from  the 
sediment  at  the  bottom  of  a  stream  and  from  the  scum  on 
the  surface.  If  a  stream  should  not  be  deep  enough  to  admit 
of  this  method  of  taking  a  sample,  dip  up  the  water  with  an 
absolutely  clean  vessel  and  pour  it  into  the  bottle  after  the 
latter  has  been  rinsed. 

The  sample  of  water  should  be  collected  immediately  be- 
fore shipping  by  express,  so  that  as  little  time  as  possible 
shall  intervene  between  the  collection  of  the  sample  and  its 
examination.  All  possible  information  should  be  furnished 
concerning  the  source  of  the  water  and  of  possible  sources  of 
contamination.  For  example,  in  the  case  of  a  well,  the  prox- 
imity of  dweUings,  cesspools,  or  drains  should  be  recorded, 
and  the  character  and  slope  of  the  soil,  whether  toward  or 
away  from  the  well,  should  be  noted.  In  the  case  of  a  sur- 
face-water, mention  any  abnormal  or  unusual  conditions;  as, 
for  instance,  if  the  streams  or  ponds  are  swollen  by  recent 
heavy  rains,  or  are  unusually  low  in  consequence  of  prolonged 
drought,  or  if  there  be  a  great  deal  of  vegetable  growth  in  or 
on  the  surface  of  the  water.  Record,  in  short,  any  circum- 
stantial evidence  which  by  any  possibility  may  aid  in  the  final 
judgment. 

The  question  of  proper  collection  of  samples  is  an  impor- 
tant one,  and  the  chemist  is  perfectly  justified  in  refusing  to 


water:   analytical  methods.  85 

give  an  opinion  in  regard  to  the  purity  of  a  water  which  he 
has  not  himself  collected.  The  ignorance  and  carelessness 
shown  by  people  who  send  samples  for  analysis  are  often- 
times quite  amusing.  Samples  have  been  received  at  this 
laboratory  in  almost  every  kind  of  container  imaginable,  from 
an  imperfectly  rinsed  whisky-bottle  to  a  discarded  syrup-jug, 
with  about  an  inch  of  maple  sugar  in  the  bottom.  One  sam- 
ple was  sent  all  the  way  from  Georgia  in  a  stone  jug  with  a 
corn-cob  inserted  for  a  stopper.  Others  are  received  with 
the  stopper  carefully  (?)  protected  by  a  mass  of  sealing-wax 
or  candle-grease.  A  favorite  way  is  to  send  the  sample  in  a 
fruit-jar  packed  in  sawdust  or  straw.  Opinions  evidently 
dififer  greatly,  too,  in  regard  to  the  size  of  sample  that  is 
needed.  It  is  no  uncommon  occurrence  to  have  a  person 
come  into  the  laboratory  with  the  remark,  "  Here  is  a  sample 
of  water  that  I  want  analyzed,"  supplemented  by  the  produc- 
tion from  a  coat-pocket  of  a  homoeopathic  vial  or  a  sample 
of  half  a  pint  or  so  of  water.  Of  course,  in  cases  like  these 
practically  nothing  can  be  done. 

Preparation  of  the  Sample  for  Analysis. — Since  changes 
in  the  composition  of  a  contaminated  water  are  constantly 
going  on,  the  analysis  of  the  sample  should  be  begun  without 
delay.  The  bottle  is  held  under  the  tap.  and  the  neck  and 
stopper  are  washed  free  from  adhering  dust.  The  stopper  is 
rinsed  off  with  some  of  the  water  from  the  bottle.  Qualita- 
tive tests  should  be  made  for  ammonia,  nitrites  and  chlorine. 
With  waters  containing  much  suspended  matter,  and  in  the 
case  of  surface-waters  in  which  it  is  desired  to  distinguish 
between  the  organic  matter  in  solution  and  that  in  suspen- 
sion, a  portion  of  the  water  should  be  filtered.  In  most 
cases  the  suspended  matter  can  be  removed  by  filtration 
through  paper.  For  this  ])ur])osc  only  tlic  best  Swedish 
rilter-])aper  should  be   used,  and   the   liltcrs  should  l)e   lirst 


S6 


AIR,    WATER,    AND    FOOD. 


thoroughly  washed  with  ammonia-free  water.  With  som^e 
waters  containing  very  finely  divided  clay  in  suspension,  fil- 
tration through  paper  will  not  be  satisfactory,  and  the  sample 
must  be  filtered  by  suction  through  a  cylinder  of  unglazed 
porcelain,  such  as  an  ordinary  Chamberland-Pasteur  filter- 
tube.  In  the  filtered  water  it  is  customary  to  determine  the 
dissolved  solids,  the  albuminoid  ammonia,  or  the  organic 
nitrogen,  and  the  color. 

Determination  of  Free  and   Albuminoid  Ammonia. — 
Apparatus. — The   apparatus   used   for   the   determination   of 

ammonia  is  that  shown 
in  Fig.  4.  It  consists 
of  a  round-bottomed 
flask  of  900  c.c.  capaci- 
ty, with  square  shoul- 
ders and  a  narrow  neck 
five  inches  long,  and  an 
ordinary  Liebig  con- 
denser fitted  with  an 
inner  tube  of  block  tin, 
^/i6  of  an  inch  in  diame- 
ter. The  flask  is  closed 
by  a  cork  carrying  a 
glass  tube  bent  nearly  at 
right  angles,  which 
slips  for  some  distance 
within  the  tin  tube  of 
the  condenser.  A  tight 
joint  is  made  by  means 
of  a  large  cork,  which 
is  shown  in  section  in 
Fig.  5.  The  large  cork 
serves  the  double  purpose  of  making  a  tight  joint  with  the 


Scale JTi  in .=  1  foot. 

Fig.  4. — Apparatus  for  Ammonia  Dis- 
tillation. 


water:  analytical  methods. 


87 


condenser  and  also  as  a  convenient  means  for  handling  the 
small  glass  tube.  In  order  to  remove  the  cork  from  the  dis- 
tilling-flask,  the  glass  tube  carrying  it  is  simply  turned  to  one 
side,  using  the  large  cork  as  a  pivot.  The  flasks  are  heated 
with  the  free  flame  of  a  Bunsen  burner. 

New  flasks  are  treated  with  boiling  dilute  sulphuric  acid 
and  potassium  bichromate  before  they  are  used.  New  corks 
should  be  steamed  out  for  one  or  two  hours.  A  good,  sound 
cork  will  last  for  several  months  with  daily  use.     The  dis- 


CORK    JOINT 

Full  Size 


Fig.  5. 

tillates  are  received  into  small  50-c.c.  flasks  and  poured  into 
Nessler  tubes  for  nesslerization.  The  Nessler  tubes  are  11 
inches  long  and  f-inch  internal  diameter,  the  50-c.c.  mark 
being  about  two  inches  from  the  top.  It  is  possible  to  so 
arrange  the  apparatus  as  to  collect  the  distillates  directly  in 
the  Nessler  tubes  where  only  one  or  two  samples  are  exam- 
ined at  a  time.  For  class  work  the  compact  form  of  appara- 
tus similar  to  that  used  in  agricultural  laboratories  for  the 
Kjeldahl  determination  is  not  so  suitable. 

Directions. — Free  the  apparatus  from  ammonia  by  dis- 
tilling off  the  water  in  the  flask,  testing  each  50-c.c.  portion 
of  the  distillate  until  no  color  is  given  with  the  Nessler  re- 
agent.    When  the  distillate  is  free  from  ammonia,  pour  the 


S8  AIR,    WATER,    AND    FOOD. 

water  left  in  the  flasks  into  the  bottle  marked  "  Ammonia- 
free  Residues." 

Shake  the  bottle  thoroughly  to  mix  the  sample,  and 
measure  out  in  a  calibrated  flask  a  portion,  usually  500  c.c, 
for  the  ammonia,  the  amount  taken  depending  upon  the  re- 
sult of  the  qualitative  test.  Pour  this  into  the  distilling- 
flask,  and  distil  over  three  portions  of  50  c.c.  each  into  the 
graduated  flasks.  Regulate  the  height  of  the  flame  so  that 
the  time  of  distilling  50  c.c.  shall  be  not  more  than  eight  and 
not  less  than  five  minutes. 

After  the  free  ammonia  has  been  distilled  off,  allow  the 
contents  of  the  flask  to  cool  slightly;  then  add  40  c.c.  of  alka- 
line permanganate  through  a  funnel  taking  care  that  none 
of  the  alkaline  solution  touches  the  neck  of  the  flask,  and  pro- 
ceed with  the  distillation  of  the  albuminoid  ammonia;  that  is 
to  say,  the  determination  of  the  nitrogen  of  the  undecomposed 
organic  matter.  With  colored  surface-waters  distil  off  five 
portions  of  50  c.c.  each;  with  waters  of  low  organic  content 
three  or  four  portions  will  suffice. 

It  is  almost  impossible  to  convert  all  of  the  organic  nitro- 
gen into  ammonia  by  boiling  with  alkaline  permanganate, 
the  amount  of  ammonia  which  is  thus  obtained  depending 
upon  the  concentration  of  the  solution  and  the  rate  of  boil- 
ing. In  order  that  the  albuminoid  ammonia  shall  bear  some 
definite  relation  to  the  total  organic  nitrogen  it  is  necessary 
that  these  conditions  shall  be  duplicated  as  nearly  as  possible 
in  different  determinations;  that  is.  the  alkaline  permanga- 
nate must  be  added  to  a  definite  volume  of  the  water,  and 
the  boiling  must  be  carried  on  at  a  definite  rate.  Some  of 
the  highly  colored  surface-waters  give  up  their  nitrogen  ver>' 
slowly  by  this  treatment,  so  that  to  distil  off  all  the  albumin- 
oid ammonia  which  these  waters  are  capable  of  yielding 
would  be  an  almost  endless  task.     It  is  much  better  to  Se 


water:   analytical  methods.  89 

content  with  the  comparative  resuks  which  can  be  obtained 
by  carrying  out  successive  determinations  under  similar  con- 
ditions. 

Have  the  Nessler  tubes  clean  and  thoroughly  rinsed,  and 
pour  into  them  the  contents  of  the  50-c.c.  receiving-flasks. 
Prepare  the  standards  by  adding  to  Nessler  tubes  nearly  filled 
with  ammonia-free  water  varying  quantities  of  the  standard 
ammonium  chloride  solution;  for  instance,  o.i.  0.3.  0.5,  0.7, 
i.o,  1.3,  1.5,  2.0,  2.5,  4.0,  6.0  c.c.  The  standard  ammonium 
chloride  solution  contains  .00001  gram  N  in  one  cubic  centi- 
meter. 

Mix  the  contents  of  the  tubes  by  rotating  them  between 
the  palms  of  the  hands  (never  shake  them  like  a  test-tube  or 
stir  them  with  a  rod),  allow  them  to  stand  for  two  or  three 
minutes  and  add  i  c.c.  of  the  Nessler's  reagent  to  the  whole 
set,  and  to  the  samples  to  be  tested,  as  rapidly  as  possible. 
At  the  end  of  ten  minutes  match  the  colors  and  record  the 
amount  of  ammonia. 

As  an  example  of  a  colored  surface-water  may  be  given 
the  following  results  from  distilling  500  c.c: 

Free  Ammonia.  Albuminoid  Ammonia. 

1st   50  c.c,     0.7  c.c                  1st    50  c.c,  4. 5  c.c 

2d    50  c.c,     0.3  c.c                  2d     50  c.c,  2.8  c.c 

3d    50  c.c,     0.0  c.c                  3d     50  c.c,  1.5  c.c. 

4th   50  c.c,  1.0  c.c 

5th   50  c.c,  0.5  c.c 


1.0  c.c.  10.3  cc. 

In  this  case  the  free  ammonia  would  be  0.020  and  the 
albuminoid  ammonia  .206  parts  per  million. 

Notes. — When  the  amount  of  ammonia  shown  by  the 
qualitative  test  is  high,  i.e.,  shows  a  color  equivalent  to  i  c.c. 


90  AIR.    WATER,    AND    FOOD. 

of  the 'Standard  ammonia  solution,  a  less  quantity  than  500 
c.c.  should  be  taken  for  the  distillation,  100  c.c.  or,  in  the  case 
of  sewage,  even  10  c.c.  being  diluted  to  500  c.c.  with  water 
free  from  ammonia.  If  the  waters  give  much  trouble  from 
bumping,  coarsely  crushed  pumice  may  be  used  in  the  dis- 
tilling-flask,  although  it  is  difficult  to  keep  it  pure  enough  for 
use  with  waters  very  low  in  ammonia.  If  pumice  is  used,  care 
should  be  taken  that  the  fragments  have  rounded  corners  to 
avoid  scratching  the  glass.  Sewage  and  soils  may  be  dis- 
tilled with  steam  in  the  apparatus  figured  on  page  92  under 
the  Kjeldahl  process. 

In  dealing  with  sew^age  or  sewage  efifiuents,  which  are 
very  high  in  free  ammonia,  if  the  ammonia  were  collected  in 
three  portions,  so  much  would  distil  over  in  the  first  portion 
that  the  color  given  with  Nessler's  reagent  would  often  be  too 
deep  to  read  or  a  precipitate  might  form.  To  avoid  this  the 
total  distillate  of  150  to  175  c.c.  is  collected  in  a  200-c.c.  grad- 
uated flask,  made  up  to  the  mark,  thoroughly  mixed  by 
pouring,  and  then  50  c.c.  of  it  taken  for  nesslerization.  In 
this  way  the  ammonia  is  distributed  more  evenly  in  the  dis- 
tillate and  the  determination  is  not  sacrificed. 

In  the  case  of  water  from  suspicious  w'ells  and  of  sewage 
effluents,  about  0.5  gram  of  freshly  ignited  sodium  carbonate 
should  be  added  before  distillation,  in  order  to  make  sure  that 
the  reaction  of  the  water  is  not  acid,  and  to  decompose  anv 
urea  which  may  be  present.  This  will  not  be  necessary  with 
ordinary  surface-waters,  as  experience  has  show-n  that  they 
almost  always  have  a  slight  alkaline  reaction. 

The  necessity  for  the  use  of  soda  will  be  readily  seen 
from  an  inspection  of  the  following  results  obtained  on  the 
distillation  of  bad  well-water: 


WATER : 

ANALYTICAL    METHODS. 

Without  SoJii. 

With  Soda. 

Free  NH3. 

Alb.  NHc 

Free  NH3. 

Alb.  NH, 

2.0 

7.0 

50  out  of 

1.0 

2.5 

3.0 

200       =     4.8 

.7 

3.0 

2.0 
I.O 

Total  =19.2 

.3 

91 


For  measuring  very  deep  colors  with  the  Nessler  reagent, 
say  above  6.0  c.c.  of  the  standard  ammonium  chloride  solu- 
tion, it  v,^ill  often  be  found  convenient  to  use  a  pair  of 
Hehner's  colorimeters,  running  ofif  a  known  amount  of  the 
solution  having  the  deeper  color  until  the  colors  match.  In 
doing  this  it  is  important  that  the  color  of  the  standard 
should  not  differ  much  from  the  color  of  the  distillate,  for 
the  depth  of  color  given  by  the  Nessler  reagent  is  not  ex- 
actly proportional  to  the  amount  of  ammonia  alone;  that  is 
to  say,  the  depth  of  color  obtained  by  nesslerizing  6.0  c.c  of 
ammonia  solution  is  more  than  twice  that  obtained  with  3.0 
c.c.  in  the  same  volume  of  water. 

In  order  to  secure  the  most  accurate  results  it  is  impor- 
tant that  the  temperature  of  the  distillates  to  be  nesslerized 
and  of  the  standards  be  the  same,  since  the  warmer  solutions 
give  a  more  intense  color  with  the  Nessler  reagent. 

The  compounds  produced  by  the  action  of  ammonia  on 
mercuric  solutions  are  considered  as  substitutions  of  i  Hg 
for  2H  in  NH4,  and  are  called  mercur-ammoniums.  Tetra- 
mercur-ammonium  iodide  (NHgoI),  the  compound  formed  by 
addition  of  the  Nessler  reagent,  is  a  brown  precipitate,  sol- 
uble in  excess  of  KI  in  the  presence  of  KOH  with  a  brown- 
ish-yellow color  proportional  within  certain  limits  to  the 
pmount  of  NH;, : 

NH,  +  (2HgL  +  2KI  +  3KOH)  =  NHgJ  +  5KI  +  3H.,0. 

Tbe  "  free  ammonia  "  in  all  probability  does  not  exist  in 
the  water  in  a  free  state  or  as  the  hydroxide;  it  is  probably 


92 


AIR,    WATER,    AND    FOOD. 


present  in  the  form  of  carbonate  or  of  chloride.  When  water 
containing  these  or  similar  compounds  of  ammonia  is  boiled, 
they  are  decomposed  and  free  ammonia  passes  off  with  the 
steam  and  is  found  in  the  distillate;  hence  the  origin  of  the 
name. 

Determination  of  Total  Organic  Nitrogen  by  the 
Kjeldahl  Process. — Directions. — Measure  500  c.c.  of  the 
water  into  a  round-bottomed  flask  of  750  c.c.  capacity  and 


Fig.  6. — Apparatus  for  Distilling  Ammonia  by  Steam. 

boil  until  about  200  c.c.  have  been  driven  off.  (The  free 
ammonia  which  is  thus  expelled  may  be  determined,  if  de- 
sired, by  connecting  the  flask  with  a  condenser.)  Allow  the 
water  remaining  in  the  flask  to  cool,  and  add  10  c.c.  of 
pure  concentrated  sulphuric  acid  free  from  nitrogen.     Mix 


WATER:  ANALYTICAL  METHODS.  93 

"by  shaking;  place  the  flask  in  an  incHned  position  on  wire 
gauze  under  the  hood  and  boil  cautiously  until  the  water  is 
all  driven  off.  Place  a  small  funnel  in  the  neck  of  the  flask 
to  prevent  the  escape  of  acid  fumes,  and  continue  the  heating 
for  at  least  half  an  hour  after  the  sulphuric  acid  becoxei 
white.  Meanwhile  rinse  out  the  distilling  apparatus  (see 
Fig.  6),  and  free  it  from  ammonia  as  usual.  Then,  after  the 
acid  in  the  digestion-flask  has  cooled,  rinse  down  the  neck 
of  the  flask  w^ith  100  c.c.  of  ammonia-free  w^ater  and  attach 
the  flask  to  the  distillation  apparatus.  Add  100  c.c.  of 
potassium  hydroxide  solution  through  the  separatory  funnel 
and  distil  off  the  ammonia  by  steam,  receiving  the  distillate 
in  a  250-c.c-  graduated  flask.  Conduct  the  distillation  rather 
slowly  until  the  first  50  c.c.  have  distilled  over,  then  distil 
more  rapidly  until  about  175  c.c.  have  been  collected.  Make 
the  volume  of  the  distillate  up  to  250  c.c.  with  ammonia-free 
water,  mix  it  thoroughly  and  take  50  c.c.  for  nesslerization. 

Notes. — The  principles  involved  in  the  method  consist  in 
the  oxidation  of  the  carbon  and  hydrogen  of  the  organic  mat- 
ter by  boiling  sulphuric  acid,  the  nitrogen  being  converted 
into  ammonia  and  held  by  the  acid  as  ammonium  sulphate. 
The  ammonia  is  then  liberated  and  distilled  off  from  an  alka- 
line  solution.  The  use  of  mercury  and  of  potassium  per- 
manganate to  assist  in  the  oxidation  has  been  found  to  be 
unnecessary,  as  the  organic  matter  in  natural  waters  is  much 
more  easily  oxidized  than  in  other  substances, — flour,  for  in- 
stance. The  presence  of  nitrates  and  nitrites  in  waters  has 
not  been  found  to  interfere  with  the  accurate  determination 
of  the  organic  nitrogen.  The  error  which  has  been  found  by 
Kjeldahl  and  Warrington  to  be  caused  by  the  presence  of 
nitrates  seems  to  disappear  when  the  organic  material  is 
diluted  to  the  considerable  extent  that  exists  in  natural 
waters.     The  high  chlorine  found  in  some  well-waters  does 


94  AIR,    WATKK,    AND    FOOD. 

not  interfere  with  the  method  to  any  extent,  but  this  deter- 
mination does  not  possess  much  vakie  in  this  class  of  waters, 
wliich  arc  low  in  organic  nitrogen. 

In  carrying  out  the  digestion  with  sulphuric  acid,  the 
greatest  care  must  be  taken  to  prevent  access  of  ammonia  or 
dust  from  any  source.  The  acid  solutions  will  absorb  am- 
monia from  the  air  or  from  the  dust  of  the  laboratory  if  they 
are  allowed  to  remain  uncovered  for  any  length  of  time. 
This  source  of  error  may  in  some  instances  be  sufficiently 
large  to  render  a  determination  valueless,  even  in  a  room 
which  is  to  all  appearances  free  from  ammonia-fumes. 
Hence  the  operation  should,  if  possible,  be  carried  to  com- 
pletion within  twenty-four  hours,  and  for  every  set  of  deter- 
minations a  blank  analysis  should  be  made  with  ammonia- 
free  water  in  order  to  make  a  correction  for  the  ammonia  in 
the  reagents,  and  for  that  accidentally  introduced  during  the 
process. 

As  the  result  of  many  hundred  comparative  determina- 
tions of  the  organic  nitrogen  and  of  the  albuminoid  ammo- 
nia in  natural  waters  which  take  their  origin  in  the  glacial 
drift,  it  has  been  found  that  the  nitrogen  given  by  the  albu- 
minoid-ammonia process  as  directed  in  the  previous  pages 
is  about  one-half  of  the  total  organic  nitrogen  as  given  by  the 
Kjeldahl  process;  in  the  case  of  sewages  and  polluted  waters 
it  may  be  only  about  a  third. 

Determination  of  Nitrogen  in  the  Form  of  Nitrites. 
— Directions. — When  the  determination  of  the  free  and 
albuminoid  ammonia  is  well  under  way,  the  estimation  of 
nitrogen  in  the  next  stage  of  decay,  that  of  nitrites,  should 
be  begun.  If  the  water  is  colorless,  measure  out  the  required 
amount,  usually  lOO  c.c,  into  a  loo-c.c.  tube.  If  the  water 
possesses  color  which  cannot  be  removed  by  simple  filtra- 
tion, it  should  be  decolorized  as  follows:   Thoroughly  rinse 


water:  analytical  methods.        95 

Avith  the  water  a  250-c.c.  glass-stoppered  bottle;  pour  into 
it  about  200  c.c.  of  the  sample,  add  about  3  c.c.  of  the  milk 
of  alumina  and  shake  the  bottle  vigorously.  Let  the  bottle 
stand  for  ten  or  fifteen  minutes  and  filter  through  a  small 
filter  wMch  has  been  thoroughly  washed  with  water  free 
from  nitrites.  Enough  should  be  filtered  for  both  the 
nitrites  and  nitrates.  At  the  same  time,  make  up  stand- 
ards by  adding  to  the  tubes  containing  about  100  c.c.  of 
nitrite-free  water  varying  amounts  of  the  standard  solution; 
for  example,  i.o,  3.0,  5.0,  and  lo.o  c.c. 

To  each  of  the  tubes  containing  the  colorless  water,  and 
to  the  standards,  add  the  following  reagents  in  the  order 
given:  i  c.c.  of  hydrochloric  acid  (1:3),  2  c.c.  of  sulphaniHc 
acid,  2  c.c.  of  naphtylamine  hydrochlorate.  Mix  thor- 
oughly, and  after  twenty  minutes  compare  the  colors.  One 
cubic  centimeter  of  the  standard  nitrite  solution  contains 
o.ooooooi  gram  N  as  nitrite.  The  determination  must  be 
completed  within  half  an  hour,  since  the  air  of  a  room  in 
wdiich  gas  is  burned  contains  nitrites.* 

Ilosvay's  Modiftcation. — Ilosvay  f  has  modified  the  method 
by  substituting  acetic  acid  for  hydrochloric  acid.  The  color 
is  developed  more  rapidly  and  the  gradation  of  color  is  more 
uniform.  The  process  is  carried  out  as  above,  except  that 
10  c.c.  of  each  of  the  reagents  (p.  207),  or  2  c.c.  for  25  c.c.  of 
the  water,  is  used,  and  the  colors  are  read  after  five  minutes. 

Notes. — If  the  color  obtained  is  more  than  that  given  by 
20  c.c.  of  the  standard  solution,  as  it  may  be  in  the  case  of 
water  from  bad  wells  and  sewage  effluents,  the  water  should 
be  diluted  with  nitrite-free  water,  10  c.c.  or  even  i  c.c.  being 
made  up  to  too  c.c.  before  adding  the  reagents,  since  colors 
above  20  c.c.  are  too  deep  for  accurate  comparison. 

*  Defren:    Tec/i.  Quart..  9  (rSgb).  238;  Axson:  loc.  cit.,  12  [rSqq),  219. 
f  Bull.  Soc.  Chitn.  [3],  2  {iSSc)),  347. 


96  AIR,    WATER,    AND    FOOD. 

The  reactions  which  lake  place  consist  first  in  the  diazotiz- 
ing  of  the  sulphanilic  acid  by  the  nitrite  present  in  acid  solu- 
tion, forming  (.liazobenzenesulphonic  anhydride.  This  reads 
with  the  naphtylamine  hydrochlorate,  forming  azo-or-amido- 
naphtylic  parabenzol-sulphonic  acid,  which  gives  the  pink 
color  to  the  solution,  the  amount  formed  depending  upon 
the  amount  of  nitrite  present. 

N  N         H 

I  1  I 

c  c       c 

/\  //\/  \ 

H— C         C— H         H— C         C         C— H 

II  I  I  II  I 

H— C         C— H         H— C         C         C— H 

\  //  \  /  \  / 

c  c       c 

I  I     I 

SO3H  NH,      H 

Determination  of  Nitrogen  in  the   Form  of  Nitrates. 

— Directions. — Nitrogen  in  the  fourth  stage,  that  of  nitrates, 
is  next  determined.  In  the  case  of  ground-waters,  measure 
two  portions,  one  of  2  c.c.  and  one  of  5  c.c,  from  the  bottle, 
with  a  capillary  pipette,  into  three-inch  porcelain  evaporating- 
dishes;  for  surface-waters,  always  low  in  nitrates,  take  10  c.c. 
from  the  portion  already  decolorized  in  the  determination  of 
the  nitrites.  Place  the  dishes  on  the  top  of  the  water-bath 
and  let  their  contents  evaporate  gently  until  one  or  tw^o  drops 
are  left;  then  set  them  away  in  a  place  free  from  dust,  that 
the  remainder  may  evaporate  spontaneously.  Do  not  let 
them  go  quite  to  dryness  on  the  bath. 

When  the  water  is  entirely  evaporated,  drop  six  drops  of 
phenol-disulphonic  acid  directly  upon  the  dry  residue  and 
rub  it  around  with  a  glass  rod  to  insure  complete  contact  of 
the  acid  and  the  residue  in  the  dish.  Dilute  the  acid  with 
7  c.c.  of  distilled  water  and  add  3  c.c.  of  the  alkali  solution. 


water:   analytical  methods.  97 

To  prepare  the  standards,  measure  out  the  required  amount 
of  the  standard  nitrate  sokition  (see  Reagents,  page  207)  from 
the  burette,  add  enough  water  to  make  the  total  vohime 
10  ex.,  and  two  or  three  drops  of  the  alkaH.  One  cubic 
centimeter  of  the  standard  sohition  contains  0.00000 1  gram 
N  as  nitrate.  The  comparison  is  best  made  in  the  small 
porcelain  dishes.  For  high  colors  the  liquids  are  compared 
in  tubes  similar  to  the  Nessler  tubes,  but  shorter. 

Notes. — It  will  be  found  that  if  10  c.c.  of  a  colored  water 
be  evaporated  directly,  the  color  obtained  with  the  reagents 
will  be  much  deeper  as  well  as  browner  than  that  given  by 
the  standards;  hence  the  necessity  for  first  decolorizing. 

Chlorine  interferes  with  the  accuracy  of  the  method,  but 
not  to  any  extent  when  present  in  less  than  20  parts  per 
million.  If  the  amount  of  chlorine  be  more  than  this,  the 
evaporation  should  be  made  in  vacuo  over  sulphuric  acid. 
Nitrites  do  not  interfere  with  the  test. 

The  reaction  is  generally  considered  to  consist  in  the 
formation  of  picric  acid.  While  this  is  not  quantitatively 
true,  it  offers  the  best  explanation  of  the  changes  that  occur. 
Trinitrophenol  (picric  acid)  is  formed  by  the  action  of  the 
nitrates  in  the  cold,  dry  residue  upon  the  phenol-disulphonic 
acid  with  which  it  is  moistened: 

OH  OH 

H—C         C— SO3H  NO-C  C— NO, 

II  I  -}-3HN03=  II  I  +2H,S0« 

H_C         C-H  H-C  C-H 

\  //  \  //  +  "^O 

c  c 

I  I 

SO,H  NO, 

phenol-disulphonic  acid.  Picric  acid. 


98  AIR,    WATER,    AND    FOOD. 

The  addition  of  an  excess  of  caustic  alkali  converts  the 
picric  acid  to  the  alkali  picrate,  which  imparts  an  intense  yel- 
low color  to  the  liquid.  The  best  color  is  obtained  by  the 
use  of  ammonia. 

Large  quantities  of  nitrates  in  colorless  water  may  be  de- 
termined by  reduction  to  ammonia  by  sodium  amalgam,  or 
by  any  reaction  which  yields  nitrogen,  this  being  measured 
as  gas. 

Determination  of  the  Carbonaceous  Matter  or  "  Oxy- 
gen Consumed." 

Kubd's  Hot  Acid  Method. 

Directions. — Measure  lOO  c.c.  of  the  water  into  a  250-c.c. 
flat-bottomed  flask;  add  8  c.c.  of  sulphuric  acid  (1:3)  and 

about  10  c.c.  of  approxmiately potassmm  permanganate. 

Place  the  flask  on  wire  gauze  and  heat  it  quickly  to  boiling. 
When  the  liquid  begins  to  boil,  introduce  a  small  air-blast  to 
prevent  bumping  and  to  avoid  too  great  a  rise  of  tempera- 
ture. Boil  the  solution  for  exactly  five  minutes;  remove  it 
from  the  flame;  let  it  cool  one  minute,  and  add  10  c.c.  of 

N 
exactly  —  oxalic  acid.     Titrate  with  the  permanganate  to 
•'100  1  f> 

a  faint  permanent  pink  color.  In  order  to  find  the  exact 
value  of  the  permanganate  solution  a  blank  determination 
must  be  carried  through  in  precisely  the  same  way,  using  loa 
c.c.  of  water  free  from  carbonaceous  matter. 

Example. — In  the  blank  determination,  10  c.c.  oxalic  acid 
requires  10.35  c.c.  permanganate.  Since  i  c.c.  of  the  oxalic 
acid  equals  0.00008  gram  of  oxygen,  i  c.c.  permanganate 
equals  0.00007729  gram. 

Suppose  100  c.c.  w'ater  -f  10  c.c.  oxalic  acid  required 
12.57  c.c.  permanganate,  then  12.57 —  10.35  =  -■--  c.c.  per- 
manganate   required    by    the    water.     2.22  X  .00007729  =; 


WATER:  ANALYTICAL  METHODS.  99 

.0001716  gram  oxygen  for  100  c.c.  water  =  1.716  parts  per 
million. 

Notes. — For  highly  colored  surface-waters  25  c.c.  are 
taken  and  diluted  to  100  c.c.  with  water  free  from  organic 
matter;  for  sewages  10  c.c.  are  diluted  in  the  same  way. 

The  oxygen  given  up  by  the  permanganate  combines 
with  the  carbon  of  the  organic  matter  and  perhaps  to  a  cer- 
tain extent  with  the  hydrogen,  but  not  with  the  nitrogen. 
The  amount  of  oxygen  consumed  bears  some  relation,  there- 
fore, to  the  amount  of  organic  carbon  present  in  the  water, 
but  this  relation  certainly  cannot  be  taken  as  a  definite  one 
in  every  case,  the  results  varying  even  with  the  time  of 
boiling.  The  method  has  its  greatest  value  when  it  is 
used  to  compare  waters  of  the  same  general  character  and 
having  the  same  origin;  for  example,  in  making  periodical 
tests  of  the  purity  of  the  efBuent  from  a  filter.  Furthermore, 
in  order  that  the  results  shall  have  this  comparative  value, 
it  is  absolutely  necessary  that  the  process  shall  always  be 
carried  out  in  exactly  the  same  way,  even  to  the  minutest 
detail  of  quantity,  time,  and  temperature. 

In  some  cases  it  may  be  found  advantageous  to  heat  the 
solution  upon  the  water-bath  for  half  an  hour  instead  of  boil- 
ing it  for  five  minutes. 

Different  kinds  of  organic  matter  behave  differently  with 
various  oxidizing  agents,  so  that  a  comparison  of  the  results 
obtained  with  different  oxidizing  agents  may  throw  light 
upon  the  character  of  the  organic  matter,  as  well  as  its 
amount.*  In  waters  from  the  watersheds  of  eastern  North 
America  the  color  and  the  oxygen  consumed  have  a  certain, 
though  somewhat  varying,  relation. 

Determination  of  Chlorine. — The  chlorine  is  deter- 
mined  in   natural   waters   by  the   method   in   general   use; 

*  Woodman:  /.  Am.  Chem.  Soc,  20  {rSgS),  497. 


100  AIR,    WATER,    AND    FOOD. 

namely,  titration  with  a  solution  of  silver  nitrate,  using-  potas- 
sium chromate  as  an  indicator.  Since  the  exact  change  of 
color  which  constitutes  the  end-point  will  vary  with  the 
sensitiveness  of  the  eyes  of  different  observers  to  red,  each 
person  should  standardize  the  silver  nitrate  solution  for  him- 
self. To  do  this,  measure  into  a  six-inch  porcelain  dish  25 
c.c.  of  distilled  water;  add  5  c.c.  of  sodium  chloride  solution 
(i  c.c.  =  o.ooi  gram  CI)  from  the  burette  and  three  drops  of 
potassium  chromate  solution.  Titrate  with  the  silver  nitrate 
solution  until  the  yellow  color  of  the  liquid  assumes  the  faint- 
est tinge  of  reddish  brown. 

Directions. — Waters  which  are  high  in  chlorine,  i.e.,  which 
contain  20  or  more  parts  per  million,  are  titrated  directly, 
using  25  c.c.  either  with  or  without  the  addition  of  5  c.c.  of 
the  salt  solution.  Waters  which  are  low  in  chlorine  are  con- 
centrated before  titration,  250  c.c.  being  evaporated  to  25  c.c. 
on  the  water-bath.  Brown  surface-waters  should  be  decol- 
orized as  follows:  Pour  into  a  750-c.c.  flat-bottomed  flask 
about  500  c.c.  of  the  water.  Add  3  c.c.  of  the  milk  of 
alumina;  shake  and  heat  the  water  quickly  to  boiling  on  an 
iron  plate.  When  the  liquid  comes  to  a  full  boil,  at  once 
remove  the  flask  from  the  plate  to  avoid  loss  by  evaporation. 
Place  it  in  an  inclined  position  to  allow  the  alumina  to  settle. 
Decant  ofif  250  c.c.  of  the  colorless  water  into  a  six-inch  dish 
for  concentration  to  25  c.c,  using  a  flask  calibrated  for  both 
the  hot  and  the  cold  solution.  Before  making  the  titration, 
rub  down  the  sides  of  the  dish  above  the  liquid  with  a  small 
quantity  of  distilled  water  free  from  chlorine,  using  a  clean 
feather.  Rinsing  alone  will  not  always  dissolve  the  chlo- 
rides which  adhere  to  the  sides  of  the  dish. 

]\[otcs. — For  titration  by  this  method  the  solution  must 
be  as  nearly  neutral  as  possible.  If  the  water  i?  alkaline  to 
any  extent,  it  should  be  neutralized  with  dilute  sulphuric  acid, 


water:  analytical  methods.  lor 

using  phenolphthalein  as  an  indicator.  The  solution  will 
then  contain  alkali  only  as  bicarbonate,  which  does  not 
interfere  with  the  titration.  Acid  water  must  be  made  neu- 
tral by  the  addition  of  sodium  carbonate. 

It  is  important  that  the  process  be  carried  out  essentially 
as  described,  since  it  has  been  found  that  the  results  vary 
with  the  volume  of  solution  in  which  the  titration  is  made, 
the  amount  of  chromate  used,  and  the  amount  of  precipitated 
silver  chloride  present.*  A  correction  for  volume  can  be 
made  by  means  of  the  formula  given  by  Hazen,  but  it  is  bet- 
ter to  carry  out  the  titration  under  similar  conditions  each 
time,  and  to  use  a  volume  of  25  c.c.  rather  than  100. 

Determination  of  the  Residue  on  Evaporation  and 
the  Loss  on  Ignition. — Directions. — Ignite  and  weigh  a 
platinum  dish.  IVIeasure  into  it  100  c.c.  of  the  water  (200 
c.c.  in  the  case  of  surface-waters),  and  evaporate  to  dryness 
on  the  water-bath.  When  the  water  is  all  evaporated  heat 
the  dish  in  the  oven  at  the  temperature  of  boiling  water  for 
two  hours,  then  let  it  remain  in  a  desiccator  over  sulphuric 
acid  for  several  hours  and  weigh. f  The  increase  in  weight 
gives  the  "  total  solids  "  or  '*  residue  on  evaporation."  If 
from  a  ground-water,  save  the  residue  for  the  determination 
of  the  iron. 

In  the  case  of  surface-waters  the  residue  should  be  ignited 
and  the  loss  on  ignition  noted.  Heat  the  dish  in  a  "  radia- 
tor," which  consists  of  another  platinum  dish  enough  larger 
to  allow  an  air-space  of  about  half  an  inch  between  the  two 
dishes,  the  inner  dish  being  supported  by  a  triangle  of  plati- 
num wire.  Over  the  inner  dish  is  suspended  a  disk  of 
platinum-foil  to  radiate  back  the  heat  into  the  dish.  The 
larger  platinum  dish  is  heated  to  bright  redness  by  a  triple 

*  Hazen:  Am.  Chetu.  four.,  il  {iSSg),  409. 

f  In  some  laboratories  it  is  the  practice  to  dry  at  110°  or  130°  C. 


102  AIR,    WATER,    AND    FOOD. 

gas-burner.  Heat  the  dish  in  the  radiator  until  the  residue  is 
white  or  nearly  so.  Note  any  ])lackening  or  charring  of  the 
residue  and  any  peculiar  "  burnt  odor  "  which  may  be  given 
off.  After  the  dish  has  cooled,  slightly  moisten  the  residue 
with  a  few  drops  of  distilled  w^ater  to  secure  weighing  under 
the  same  conditions.  Heat  the  residue  in  the  oven  for  half  an 
hour;  cool  in  a  desiccator  and  weigh.  This  gives  the  weight 
of  "  fixed  solids."  the  difference  being  the  "  loss  on  ignition." 

Notes. — Before  the  introduction  of  modern  methods  of 
water-analysis  the  determination  of  "  loss  on  ignition  "  was 
the  only  method  for  the  estimation  of  organic  matter  in 
water.  In  order,  however,  that  the  determination  shall  pos- 
sess any  real  value,  it  is  necessary  to  regulate  carefully  the  heat 
during  the  ignition,  so  as  to  destroy  the  organic  matter  with- 
out decomposing  calcium  carbonate  or  volatilizing  the  alkali 
chlorides. 

This  is  what  the  use  of  the  radiator  is  intended  to  accom- 
plish, and  in  the  case  of  surface-waters,  wath  low  mineral  con- 
tent and  considerable  organic  matter,  the  method  gives  gen- 
erally satisfactory  results.  But  in  the  case  of  ground-waters 
having  little  or  no  organic  matter  and  high  mineral  content 
the  loss  is  often  very  great  on  account  of  the  decomposition 
of  nitrates  and  chlorides  of  the  alkaline  earths  and  the  loss  of 
water  of  crystallization.  In  waters  of  this  class  the  determi- 
nation of  "  loss  on  ignition  "  is.  therefore,  generally  meaning- 
less, although  an  approximation  to  the  amount  of  organic 
matter  can  be  obtained  by  the  addition  of  sodium  carbonate  to 
the  water  before  evaporating  to  dryness.  By  this  means  the 
alkaline  earths  are  precipitated  as  carbonates,  the  chlorine 
and  nitric  acid  are  held  by  an  alkaline  base,  and  t'here  is  no 
water  of  crystallization  in  the  residue.  Even  with  this  modi- 
fication the  loss  is  considerable  when  magnesium  salts  are 
present,  owing  to  the  loss  of  carbonic  acid. 


water:  analytical  methods.       103 

The  behavior  on  ignition  is  oftentimes  significant. 
Swampy  or  peaty  waters  give  a  brownish  residue  on  evapora- 
tion to  dryness,  which  blackens  or  chars,  and  this  black  sub- 
stance burns  off  quite  slowly.  The  odor  of  the  charring  is 
like  that  of  charring  wood  or  grain;  sometimes  sweetish,  but 
not  at  all  offensive.  Waters  much  polluted  by  sewage  blacken 
slightly;  the  black  particles  burn  off  quickly  and  the  odor  is 
disagreeable.  Any  observations  on  this  point  should  be  re- 
corded in  the  report  (p.  120)  under  the  heading  "  Change  on 
Ignition." 

Determination  of  the  Hardness. 

I.  By  Soap.— Clark's  Method. 
Directions. — IMeasure  50  c.c.  of  water  into  a  200-c.c.  clear 
glass-stoppered  bottle  and  add  the  soap  solution  from  the 
burette,  two  or  three  tenths  of  a  cubic  centimeter  at  a  time, 
shaking  well  after  each  addition,  until  a  lather  is  obtained 
which  covers  the  entire  surface  of  the  liquid  with  the  bottle 
lying  on  its  side,  and  is  permanent  for  five  minutes.  The 
number  of  parts  of  calcium  carbonate  corresponding  to  the 
volume  of  soap  solution  used  is  found  in  the  table  in  Appen- 
dix A. 

This  will  give  the  total  hardness.  If  it  is  desired  to  find 
the  permanent  hardness  also,  dilute  50  c.c.  of  the  water  to 
about  200  c.c.  and  boil  down  to  50  c.c.  in  a  beaker,  cool  and 
determine  the  hardness  as  before.  This  will  give  the  per- 
manent hardness,  and  the  difference  will  be  the  temporary 
hardness. 

Notes. — When  potassium  or  sodium  soap  is  added  to 
water  containing  calcium  and  magnesium  salts,  the  soap  is 
decomposed,  and  insoluble  compounds  with  the  fatty  acids 
are  formed.  The  importance  of  adding  the  soap  /;/  small  quan- 
tifies cannot  be  too  strongly  emphasized,  especially  in  the 
presence  of  magnesium  compounds.     The  presence  of  mag- 


104  AIR,    WATER,    AND   FOOD. 

nesium  salts  will  be  recognized  by  the  peculiar  curdy  appear- 
ance of  the  precipitate  formed  and  by  the  occurrence  of  a 
false  end-point,  the  lather  lasting  about  three  minutes  when 
the  titration  is  about  half  done.  If  much  carbonic  acid  be 
liberated,  it  is  better  to  follow  Dr.  Clark's  original  directions 
and  remove  it  by  suction.  ^ 

By  reference  to  the  table  it  will  be  observed  that  values 
are  not  given  for  more  than  i6  c.c.  of  the  soap  solution.  If 
in  any  case  the  water  under  examination  requires  more  than 
lo  c.c.  of  the  standard  soap  solution,  a  smaller  portion  of 
25  c.c,  ID  c.c.  or  even  2  c.c,  as  the  case  may  require,  is  meas- 
ured out  and  made  up  to  a  volume  of  50  c.c.  with  recently 
distilled  water.  If  the  volume  of  soap  used  is  qlways  about 
7  c.c,  this  will  keep  the  results  comparable  with  each  other, 
although  the  element  of  dilution  introduces  an  error.  Potable 
waters,  in  the  eastern  United  States,  at  least,  are  rarely  so 
high  in  mineral  matter  as  to  require  excessive  dilution.  In 
the  case  of  extremely  hard  waters,  however,  the  acid 
method  is  to  be  preferred.  Distilled  water  itself,  containing 
no  calcium  salt  whatever,  requires  the  use  of  a  considerable 
quantity  of  soap  to  produce  a  permanent  lather.  The  cause 
for  this  seems  to  exist  in  the  dissociation  of  the  greater  part 
of  the  soap  at  the  extreme  dilution  to  which  it  is  subjected, 
and  the  slow  accumulation  of  a  sufficient  quantity  of  undis- 
sociated  soap  to  allow  of  the  increase  of  surface  tension  to  a 
point  at  which  soap-bubbles  will  persist. 

By  the  temporary  hardness  of  water  is  meant  the  hardness 
which  is  removed  by  boiling.  It  is  due  to  the  carbonates  of 
calcium  and  magnesium  held  in  solution  by  the  carbonic  acid 
in  the  water,  probably  in  the  form  of  bicarbonates.  Perma- 
nent hardness  is  that  which  is  not  removed  by  boiling.  It  is 
caused  by  the  presence  of  soluble  salts  of  calcium  and  mag- 
nesium, not  carbonates,  but  chlorides  and  sulphates  princi- 
pally, held  in  solution  by  the  solvent  power  of  the  water  itself. 


shaking  and  add  -^  sulphuric  acid  from  the  burette  in  small 


water:   analytical  methods.  105 

2.  By  Acid. — Hchner's  Method. 

Directions. — For  the  determination  of  the  temporary  hard- 
ness or  ■■  alkalinity,"  measure  100  c.c.  of  the  water  into  a 
bottle  such  as  is  used  for  the  soap  test,  and  add  2.5  c.c.  of  the 
erythrosine  indicator  and  5  c.c.  of  chloroform.     Mix  well  by 

N_ 

50 

quantities,  shaking  thoroughly  after  each  addition.    The  pink 

color  gradually  grows  lighter  until  the  addition  of  a  drop  or 

two  of  the  acid  causes  it  to  disappear  entirely.     Each  tenth 

of  a  cubic  centimeter  of  acid  used  represents  one  part  of 

CaCOa  in  1,000,000.    Make  a  correction  for  the  indicator  by 

carrying  out  a  blank  determination  with  distilled  water. 

For  the  permanent  hardness  measure  out  100  c.c.  of  the 

N 
water  and  add  to  it  more  than  enough  —  sodium  carbonate 

50 

solution  to  decompose  the  calcium  and  magnesium  chlorides, 
sulphates,  and  nitrates  present.  Generally  50  to  100  c.c.  will 
be  sufficient.  Evaporate  the  mixture  to  dryness  in  a  plati- 
num or  nickel  dish  and  dissolve  the  residue  in  a  little  recently 
boiled  distilled  water.    Filter  through  a  small  filter  and  titrate 

N 
the  filtrate  and  washings  with  —  sulphuric  acid,  usmg  ery- 
throsine as  indicator.    The  difTerence  between  the  number  of 
cubic  centimeters  of  sodium  carbonate  used  and  the  acid  re- 
quired for  the  residue  will  give  the  permanent  hardness. 

Azotes. — This  method  is  especially  useful  for  waters  which 
require  clarification  by  alumina  and  subsequent  filtration. 
Lacmoid  and  phcnacetolin  can  also  be  used  in  the  determi- 
nation of  the  alkalinity,  l)ut  they  necessitate  titration  in  a  hot 
solution  on  account  of  their  susceptibility  to  carbonic  acid. 
The  addition  of  chloroform  when  using  erythrosine  is  to  re- 


106  AIR,    WATER,    AND    FOOD. 

move  the  non-ionized  iodeosine  molecule  as  rapidly  as  it  is 
formed  by  the  addition  of  acid.  When  it  is  thus  removed  the 
neutralization  of  the  alkali  is  at  once  apparent  and  hence  a 
sharp  end-point  is  obtained.* 

If  a  water  contains  sodium  or  potassium  carbonate  there 
will  not  be  any  permanent  hardness  and  hence  more  acid  will 
be  required  for  the  filtrate  than  corresponds  to  the  amount 
of  sodium  carbonate  added.  From  the  excess,  the  amount  of 
sodium  carl)onate  in  the  water  may  be  determined.  Any 
alkali  carbonate  present  would  be  calculated  as  temporary 
hardness  by  the  direct  titration;  hence  it  should  be  calcu- 
lated to  calcium  carbonate  and  subtracted  from  the  results 
found  by  the  direct  titration. 

Determination  of  Iron.f — Directions. — Evaporate  lOO  or 
200  c.c.  of  the  w^ater  to  dryness  in  a  platinum  dish.  (The 
weighed  residue  from  the  determination  of  total  solids  may 
be  used  if  desired.)  Treat  the  residue  with  5  c.c.  of  hydro- 
chloric acid  (1:1),  being  careful  to  carry  the  acid  to  the  edge 
of  the  dish.  In  some  cases  it  may  be  necessary  to  heat  the 
dish  gently  on  the  w^ater-bath  in  order  to  bring  all  the  iron 
into  solution.  When  all  is  dissolved  with  the  exception  of 
silica,  rinse  the  solution  into  a  loo-c.c.  tube  and  make  it  up 
to  about  50  c.c.  with  distilled  water.  Add  a  solution  of  po- 
tassium permanganate  drop  by  drop  until  the  solution  re- 
mains pink  for  ten  minutes. 

Meanwhile  prepare  a  blank  standard  with  50  c.c.  of  dis- 
tilled water  and  about  a  cubic  centimeter  of  hydrochloric 
acid.  Add  15  c.c.  of  potassium  sulphocyanide  solution  to 
the  waters  and  to  the  blank  standard.  Add  the  standard  iron 
solution,  in  small  quantities,  .02  c.c.  if  necessary,  from  a  capil- 
lary pipette,  mixing  thoroughly  by  pouring  the  solution  back 

*  Ellms:  /.  Am.  Chem.  Soc,  21  {i8gg),  359. 
f  Thomson:  /.  Chem.  Soc,  67  {iS8s),  493- 


water:  analytical  methods.  107 

and  forth  from  one  tube  to  another  after  each  addition,  until 
the  color  of  the  standard  matches  that  of  the  water.  One 
cubic  centimeter  of  the  standard  iron  solution  is  equal  to 
0.0001  gram  of  Fe. 

Notes. — In  the  case  of  some  river-waters  it  will  be  found 
necessary  to  add  a  few  cubic  centimeters  of  hydrochloric  acid 
to  the  water  while  evaporating,  in  order  to  facilitate  the  solu- 
tion of  the  iron.  This  should  be  done  on  a  separate  portion 
from  that  used  for  the  determination  of  total  solids. 

The  colors  should  be  matched  immediately  after  adding 
the  sulphocyanide,  since  the  color  fades  appreciably  on  stand- 
ine.  The  hisihest  standard  should  not  contain  more  than 
3  c.c.  of  the  iron  solution,  since  the  color  then  becomes  too 
deep  for  accurate  comparison. 

Determination  of  the  Dissolved  Oxygen. 

MctJiod  of  L.  W.  Winkler^ 

Collection  of  Samples. — The  samples  are  collected  in 
glass-stoppered  bottles  of  known  capacity,  holding  about  250 
cubic  centimeters.  When  water  is  taken  from  a  faucet  the 
bottle  is  filled  by  means  of  a  tube  which  passes  to  the  bottom 
of  the  bottle.  A  considerable  amount  of  water  is  allowed  to 
pass  through  the  bottle  and  overflow  at  the  top.  It  will  be 
almost  impossible  to  obtain  duplicate  samples  unless  the  bot- 
tles are  filled  at  the  same  time  by  means  of  a  T  tube,  owing 
to  variations  in  pressure  in  the  pipes. 

In  taking  samples  from  a  stream  or  pond,  a  stopper  with 
two  holes  is  used.  A  tube  passing  through  one  of  these  holes 
is  sunk  in  the  water  to  the  desired  depth,  and  the  other  is  con- 
nected with  a  larger  bottle  of  at  least  four  times  the  capacity 
of  the  smaller  one,  and  fitted  in  the  same  way.     From  the 

*  Berickte,  21  {r8S8),  2843. 


I08    ■  AIR,    WATER,    AND    FOOD. 

larger  bottle  the  air  is  exhausted  by  the  lungs  or  by  an  air- 
pump  until  it  is  nearly  filled  with  water.  Unless  the  determi- 
nation is  to  be  made  at  once,  the  rubber  stopper  of  the  smaller 
bottle  is  quickly  replaced  by  the  glass  stopper  so  that  no 
air  is  left  in  the  bottle.  The  temperature  of  the  water  at  the 
time  of  sampling  should  l)e  noted.  This  can  be  conveniently 
done  at  the  depth  at  which  the  sample  is  taken,  by  means  of 
a  thermometer  fitted  by  a  doubly  perforated  stopper  to  a  bot- 
tle of  about  500  c.c.  capacity  which  has  been  filled  with  some 
of  the  water  and  then  lowered  to  the  desired  depth.  An  in- 
strument capable  of  giving  more  accurate  readings  is  the 
"  thermophone  "  of  Whipple  and  Warren.* 

The  Determination. — Remove  the  stopper  and  add  2  c.c. 
of  manganous  sulphate  solution  with  a  pipette  having  a  long 
capillary  point  reaching  to  the  bottom  of  the  bottle,  and  in 
the  same  way  add  2  c.c.  of  a  solution  of  sodium  hydroxide 
and  potassium  iodide.  Insert  the  glass  stopper,  leaving  no 
Imbbles  of  air,  and  mix  the  contents  of  the  bottle.  Allow 
the  precipitate  to  settle  and  add  2  c.c.  of  strong  hydrochloric 
acid  with  another  pipette.  When  the  precipitate  is  nearly  all 
dissolved,  rinse  out  the  contents  of  the  bottle  into  a  fiask  and 

titrate  the  liberated  iodine  with  approxmiately  -—  sodium 

thiosulphate  until  the  color  becomes  a  faint  yellow.  Then 
add  starch  solution  and  titrate  to  the  disappearance  of  the 
blue  color.  The  first  end-point  should  be  taken,  as  the  color 
will  return  on  account  of  the  reducing  action  of  the  organic 
matter  present.  Determine  the  exact  normality  of  the  thio- 
sulphate solution  by  standardizing  it  against  a  solution  of 
potassium  bichromate  (i  c.c.  equals  0.001  gram  iodine)  as 
directed  on  page  176. 


*/.  N.  E.   Water  Works  Assoc,  9  (iSgs),  203. 


water:  analytical  methods.  109 

N 
Calculation  of  the  Results. — i  c.c.  - — sodium  thiosulphate 

100  ^ 

=^  0.055825  c.c.  oxygen  at  0°  and  760  mm.  (This  value  would 
ordinarily  be  corrected  for  the  barometric  pressure,  but  the 
correction  falls  within  the  limits  of  experimental  error.)  Find 
the  volume  of  oxygen  by  substitution  in  the  following  for- 
mula: 

n  X  0.055825  X  1000  . 

A  = ;: =:c.c.  oxygen  m  1000  c.c.  of  water, 

N 

where  n  =  number  of  c.c.  of  exact thiosulphate,  and  v  = 

100  ^ 

the  volume  of  the  bottle  minus  4  c.c.  (lost  by  addition  of  rea- 
gents). The  results  are  reported  in  "'  per  cent,  of  saturation," 
which  is  found  by  dividing  A  by  the  number  of  c.c.  of  oxygen 
taken  up  by  1000  c.c.  of  water  when  saturated  at  the  given 
temperature.     (See  Winkler's  table,  Appendix  A.) 

N       ,  .       ,   , 
For  example,   30.4  c.c.    7^   thiosulphate  were  used  to 

titrate  the  iodine  liberated  by  the  oxygen  in  265.5  c.c.  of  the 
water.    Temperature  of  sample  was  9°  C.    Then 

_  30.4  X  0.055825  X  1000 
~  265.5-4 

=  6.491  c.c.  oxygen  in  1000  c.c.  of  water. 

From  the  table,  1000  c.c.  water  at  9°  C.  dissolves  8.063 

6.491 
c.c.  oxygen.     Hence  the  "  per  cent,  of  saturation  "  =  ^ — ^ 

=  80.50  per  cent. 

Notes. — This  determination  is  a  good  illustration  of  an 
indirect  volumetric  process.  A  precipitate  of  manganous 
hydroxide  is  formed  in  the  bottle  by  the  reaction  of  the 
manganous  sulphate  and  the  sodium  hydroxide.  This  imme- 
diately combines  with  the  oxygen  in  the  water  to  form  a  cer- 


no  AIR,    WATER,    AND    FOOD. 

tain  amount  of  manganic  hydroxide.  The  liydrochloric  acid 
which  is  added  reacts  with  the  manganic  hydroxide  to  form 
chlorine,  whicli  in  turn  liberates  iodine  from  the  potassium 
iodide,  the  amount  thus  set  free  depending  primarily  upon 
the  quantity  of  oxygen  dissolved  in  the  water.  The  presence 
of  considerable  amounts  of  organic  matter  or  of  nitrites  in- 
troduces an  error.  In  such  cases  the  method  must  be  modified 
or  a  correction  made.  Details  of  the  method  used  in  such 
cases  are  given  in  the  paper  by  Winkler  previously  cited. 

A  correction  is  made  for  the  volume  of  the  reagents 
added,  but  if  the  precipitated  hydroxides  had  settled  before 
the  acid  was  added,  no  allowance  should  be  made  for  the 
amount  of  acid,  since  the  water  it  displaces  contains  neither 
oxygen  nor  iodine. 

If  water  is  collected  in  the  ordinary  way  and  transferred 
to  the  apparatus  by  pouring,  there  will  inevitably  be  an  ab- 
sorption of  oxygen  unless  the  water  is  already  saturated. 
Thus  a  process  which  gives  excellent  results  when  the  water 
is  nearly  or  quite  saturated  may  fail  entirely  to  give  accurate 
results  when  the  dissolved  oxygen  is  low  or  absent.  The 
water  may  be  supersaturated  with  oxygen,  in  which  case  the 
per  cent,  of  saturation  may  be  more  than  one  hundred.* 

Determinations  of  dissolved  oxygen  in  ponds  and  streams 
are  best  made  on  the  spot.  The  very  simple  apparatus  re- 
quired for  the  Winkler  process  can  be  packed  in  small  space, 
and  the  entire  determination  requires  only  a  few  minutes. 
The  absorption  of  the  oxygen  by  the  manganous  hydroxide 
is  complete  almost  at  once,  and  it  is  unnecessary  to  allow  it 
to  settle  for  a  long  time  before  adding  the  acid.  The  titra- 
tion can  be  made  with  a  small  burette  or  pipette  with  accurate 
results. 

*  Gill:    TicA.  Quart.,  5  (1^92),  250. 


water:    analytical    methods.  Ill 

Determination  of  Free  Carbonic  Acid. — Directions. — 
Measure   lOO  c.c.  of  water  into  a  flask,  add    lo  drops  of 

N 
phenolphthalein  solution  and  titrate  with  —  sodium  car- 
bonate solution  until  a  faint  permanent  pink  color  is  pro- 
duced. To  obtain  the  exact  value  make  a  second  titration, 
running  in  the  sodium  carbonate  rapidly  until  near  the  end 
and  then  drop  by  drop  until  the  exact  point  is  reached.  The 
pink  color  will  disappear  rather  slowly  near  the  end.  One 
cubic  centimeter  of  the  sodium  carbonate  solution  =  0.44 
milHgram  of  CO2. 

Note. — The  reaction  consists  in  the  formation  of  acid  so- 
dium carbonate: 

Na^COs  +  H,0  H-  CO,  =  2NaHC0, 

The  acid  carbonate  does  not  give  a  pink  color  with  phenolph- 
thalein. Sodium  hydroxide  can  also  be  used  for  the  titration, 
but  the  sodium  carbonate  solution  is  preferable. 

Determination  of  the  Color. — The  amount  of  color  is 
generally  determined  by  direct  comparison  of  the  water  with 
some  definite  standard  of  color.  Various  standards  of  color 
have  been  proposed,  the  objection  to  most  of  them  being  that 
they  are  not  sufficiently  general  in  their  application,  being 
adapted  only  for  the  color  of  some  particular  class  of  waters. 

Nesslerized  Ammonia  Standards. — The  yellowish-brown 
tint  of  the  surface-waters  of  the  Atlantic  watershed  corre- 
sponds, except  in  the  lowest  grades,  very  closely  to  that  of 
nesslerized  ammonia,  so  that  the  standards  for  reading  am- 
monia can  be  used  also  for  the  determination  of  the  color. 
The  comparison  is  made  in  the  same  kind  of  50-c.c.  tubes 
that  are  used  for  the  ammonia  determinations,  but  the  tubes 
used  for  this  purpose  are  kept  separate  from  those  used  for 
the  ammonia,  since  the  least  amount  of  alkali  remaining  in 


112  AIR,    WATER,    AND    FOOD. 

a  tube  (from  imperfect  washing,  for  instance)  alters  the  color 
of  the  water.  The  scale  used  corresponds  quite  closely  with 
the  amount  of  the  standard  ammonium  chloride  solution  in 
the  standards.  Thus  a  color  of  i.o  is  nearly  the  same  as  that 
produced  by  the  nesslerization  of  i  c.c.  of  the  standard 
ammonia;  o.i  is  about  the  color  produced  with  o.i  c.c.  of 
the  ammonia  solution.  In  the  higher  grades  of  color,  above 
1.0  or  2.0,  the  tint  varies  considerably  from  that  of  the  nes- 
slerized  ammonia,  and  the  degree  of  color  is  then  better  de- 
termined in  wider  tubes  and  in  less  depth. 

The  degree  of  correspondence  of  the  ammonia  standards 
with  the  natural  waters  is  dependant  largely  upon  the  sensi- 
tiveness of  the  Nessler's  reagent,  a  solution  which  is  so  sen- 
sitive as  to  precipitate  in  two  hours,  matching  the  colors  more 
closely  than  one  which  will  remain  for  twenty-four  hours. 
This  is  perhaps  due  to  the  reddish  tinge  given  to  the  solution 
by  the  incipient  precipitation  of  the  mercuric  iodide. 

Natural  Water  Standards. — To  avoid  these  variations  in 
color,  standards  made  from  dark-colored  water  from  swamps 
by  various  degrees  of  dilution,  and  verified  by  direct  com- 
parison with  suitably  prepared  nesslerized  ammonia  stand- 
ards, are  used.  They  have  the  same  hue  as  the  waters  to  be 
matched,  as  well  as  a  degree  of  turbidity  which  corresponds 
well  with  that  of  surface-waters;  once  prepared,  they  will 
keep  for  a  fairly  long  time  if  protected  from  the  light  and 
from  the  dust.  These  are  the  standards  that  are  in  use  in  this 
laboratory. 

Platinum  Standards. — For  ground-waters,  which  have 
only  very  little  color  and  considerable  hardness,  and  for  fil- 
tered waters,  the  platinum  color  standards  are  convenient.* 
According  to  this  scale,  the  color  of  a  water  is  the  amount  of 

*  Hazen:  Am.  Chem.  J.,  14  {i8g2),  300. 


water:  analytical  methods.  113 

platinum  in  parts  per  ten  thousand,  which,  together  with 
enough  cobalt  to  match  the  tint,  must  be  dissolved  to  pro- 
duce an  equal  color  in  distilled  water.  In  practice,  a  stand- 
ard having  a  color  of  5.00  is  prepared  by  dissolving  1.246 
grams  of  potassium  platinic  chloride  (equivalent  to  .5  gram 
platinum),  i.ooo  gram  of  cobalt  chloride  (equivalent  to  .25 
gram  cobalt),  and  100  c.c.  of  strong  hydrochloric  acid  in  dis- 
tilled water  and  diluting  to  one  liter. 

Dilute  standards  for  use  are  made  by  diluting  varying 
amounts  of  this  standard  to  50  c.c.  with  distilled  water.  Thus, 
by  diluting  i  c.c,  2  c.c,  and  3  c.c  to  50  c.c,  colors  of  o.i,  0.2, 
and  0.3  are  obtained.  It  is  claimed  that  the  platinum  stand- 
ards are  permanent  if  protected  from  the  dust. 

Iodine  Standards. — A  standard  for  color  which  could  be 
made  up  at  the  moment  when  wanted  and  without  the  use  of 
costly  apparatus  would  be  a  desideratum.  Experiments  made 
in  this  laboratory  indicate  that  an  aqueous  solution  containing 
a  definite  weight  of  iodine  offers  the  best  solution  of  the  prob- 
lem. Owing,  however,  to  the  volatility  of  iodine  even  in 
dilute  aqueous  solution  it  is  better  to  liberate  it  directly  in 
the  comparison-tube  itself.  For  this  the  following  solutions 
are  required:  Potassium  iodide,  o.i  gram  per  liter;  potas- 
sium bichromate,  0.09  gram  per  liter;  picric  acid,  0.2  gram 
per  liter. 

For  a  color  of  5.0,  50  c.c.  each  of  the  iodide  and  of  the 
bichromate  solutions  are  used;  for  lower  colors  proportional 
amounts  are  taken  and  diluted  to  100  c.c.  with  distilled  water. 
To  each  tube  is  added  i  c.c.  of  the  picric  acid  solution,  and 
just  before  the  colors  are  to  be  matched  add  2  c.c.  of  strong 
suli)hnric  acid.  The  color  develops,  as  in  the  case  of  nessler- 
ized  ammonia,  within  ten  minutes  and  can  be  relied  upon 
for  about  half  an  hour.  A  very  slight  milkiness  aids  in  match- 
ing the  color;   a  great  hindrance  to  the  use  of  metallic  sola- 


I  14  AIR,    WATER,    AND    FOOD. 

tions  being  their  clearness  or  brightness  as  compared  with 
natural  waters. 

The  comparison-tubes  which  give  the  most  satisfactory 
results  with  colors  from  5.0  to  0.5  on  the  natural  water  scale 
are  ^Vic  i"ch  wide  and  9 V4  inches  high  to  the  loo-c.c.  mark, 
For  lower  colors,  narrower  tubes,  ^  Vic  inch  diameter  and  the 
same  depth,  give  closer  readings. 

Determination  of  the  Odor. — Cold. — Shake  violently 
the  sample  in  one  of  the  large  collecting-l^ottles  when  it  is 
about  half  or  two-thirds  full,  then  remove  the  stopper  and 
quickly  put  the  nose  to  the  mouth  of  the  bottle.  Note  the 
character  and  degree  of  intensity  of  the  odor,  if  any.  An 
odor  can  often  be  detected  in  this  way  which  would  be  en- 
tirely inappreciable  if  the  water  were  poured  into  a  tumbler. 

Hot. — Pour  into  a  beaker  al^out  five  inches  high  enough 
water  to  one-third  till  it.  Cover  the  beaker  with  a  well-fitting 
watch-glass  and  place  it  on  an  iron  plate  which  has  been  pre- 
viously heated,  so  that  the  water  shall  quickly  come  to  a  boil. 
When  the  air-bubbles  have  all  been  driven  off  and  the  water 
is  about  to  boil,  take  the  beaker  from  the  plate  and  allow  it 
to  cool  for  about  five  minutes.  Then  shake  it  with  a  rotary 
movement,  slip  the  watch-glass  to  one  side  and  put  the  nose 
into  the  beaker.  Note  the  odor  as  before.  The  odor  may  or 
may  not  be  the  same  as  that  of  the  water  when  cold;  it  can 
be  perceived,  as  a  rule,  for  only  an  instant. 

JSIotes. — It  is  inevitable  that  a  certain  personal  equation 
should  influence  this  test.  Each  laboratory  will  have  its  own 
standards  for  routine  work,  but  a  certain  familiarity  with  the 
more  common  odors  will  tend  to  allay  public  anxiety  and  to 
aid  in  a  more  watchful  habit  on  the  part  of  consumers.  Good 
ground-waters  do  not  give  distinct  odors  unless  they  are  de- 
rived from  clayey  soil,  but  the  odor  often  betrays  a  contami- 
nated well  more  surely  than  any  other  test.     Surface-waters 


WATER:    ANALYTICAL    METHODS.  II5 

will  nearly  always  yield  a  characteristic  odor.  This  odor  may 
be  due  to  the  organic  matter  contained  in  the  water,  or  to 
the  presence  of  minute  plants  or  animal  organisms. 

Among  the  odors  which  are  frequently  met  are  the 
"  earthy,"  "  vegetable,"  "  musty,"  "  mouldy,"  "  disagree- 
able," and  "  offensive."  The  "  earthy "  odor  is  that  of 
freshly  turned  clayey  soil.  ''  Vegetable "  is  the  odor  of 
many  normal  colored  surface-waters;  it  may  be  described 
as  swampy  or  marshy,  pond-like,  and  is  often  strengthened 
by  heating.  "  Musty  "  can  be  likened  to  the  odor  of  damp 
straw  from  stables;  it  is  fairly  characteristic  of  sewage  con- 
tamination, and  by  the  trained  observer  is  distinctly  distin- 
guishable from  the  mouldy  odor.  "  Mouldy  "  is  the  odor  of 
upturned  garden  or  forest  mould,  or  of  a  moist  hot-house; 
it  is  somewhat  allied  to  the  earthy  odor.  "  Disagreeable  " 
is  a  term  which  is  capable  of  wide  variation  among  different 
observers.  It  may  include  certain  characteristic  odors  which 
are  peculiar  to  the  growth  or  decay  of  certain  organisms,  as 
the  "  pigpen  "  odor  of  Anabcuna,  the  '*  fishy  "  or  "  cucum- 
ber "  odor  of  Syiuira,  etc.  The  term  "  ofTensive  "  is  generally 
reserved  for  the  sewages.  These  terms  can  be  taken  only  as 
broad  illustrations  of  the  character  of  the  particular  odor, 
since  the  odor  will  very  likely  be  described  by  different  per- 
sons in  different  ways,  and  each  laboratory  will  have  its  own 
characterization.  The  odor  which  often  accompanies  an 
abundant  development  of  diatoms  is  a  good  illustration  of 
this.  It  will  be  called  by  various  inexperienced  observers 
offensive,  rotten,  fishy,  geranium-like,  aromatic,  in  one  and 
the  same  sample  of  water. 

The  terms  generally  used  to  signify  the  degree  of  inten- 
sity of  the  odor  are  "  very  faint."  "  faint,"  "  distinct,"  and 
"  decided."  The  exact  value  to  be  placed  on  each  of  these 
terms  will,  as  a  matter  of  course,  vary  with  the  indixidual 


Il6  AIR,    WATER,    AND    FOOD. 

analyst,  but  in  a  general  way  it  may  be  said  that  the  "  very 
faint  "  odor  is  one  that  would  not  be  detected  except  by  the 
trained  observer;  the  "  faint  "  odor  would  be  recognized  by 
the  ordinary  consumer  if  his  attention  were  called  to  it;  the 
"  distinct  "  odor  is  one  that  would  be  readily  noticed  by  the 
average  consumer,  but  would  not  interfere  with  the  use  of 
the  water;  while  the  "  decided  "  odor  is  one  which  would,  in 
all  probability,  render  the  use  of  the  water  unpleasant. 

Biological  Examination — The  close  relation  of  the  odor 
to  the  living  fauna  and  flora  of  the  water  makes  it  desirable 
that  the  chemist  shall  be  able  to  recognize  the  more  common 
forms  of  water  plants  and  animals  even  if  he  makes  no  pre- 
tensions to  a  knowledge  of  cryptogamic  botany  or  of  zo- 
ology. Therefore  a  microscope  and  a  concentration  appara- 
tus should  be  in  every  water-laboratory.  A  full  description 
will  be  found  in  Whipple.* 

The  bacteriological  examination  belongs  to  the  expert 
rather  than  to  the  student,  certainly  in  the  present  state  of 
our  knowledge  of  the  lower  organisms.  It  may  be  desirable 
for  the  student  to  be  familiar  with  the  simpler  methods  of 
plate  and  tu1:ie  culture,  and  the  water-works  laboratory 
should,  as  in  the  above  case,  be  provided  with  means  for  plain 
number  counts,  and  directions  for  avoiding  errors  due  to 
variations  in  temperature,  time  of  culture,  etc.  A  book  to  be 
recommended  is  Frankland's  "  Micro-organisms  in  Water." 

Determination  of  the  Turbidity  and  Sediment. — The 
suspended  matter  remaining  in  the  water  after  it  has  rested 
quietly  in  the  collecting-bottle  for  twelve  hours,  or  more,  is 
called  its  turbidity,  and  that  which  has  settled  to  the  bottom 
of  the  bottle,  its  sediment. 

Good  ground-waters  are  often  entirely  free  from  turbidity 

*  "  Microscopy  of  Drinking-water."     N.  Y.,  Wiley,  1809. 


water:   analytical  methods.  117 

and  sediment,  the  suspended  matters  having  been  filtered  out 
during  the  subterranean  passage  of  the  water,  but  this  is 
rarely  true  of  surface-waters.  The  turbidity  is  various  in 
character  and  amount,  sometimes  milky  from  clay  or  ferrous 
iron  in  solution ;  usually  it  consists  of  fine  particles,  generally 
living  algae  or  infusoria.  These  often  collect  on  the  side 
toward  or  from  the  light,  and  a  practised  eye  can,  not  infre- 
quently, recognize  their  forms.  Some  of  the  lower  animal 
forms  can  also  be  seen  by  the  naked  eye,  and  the  larger  En- 
tomostraca  are  quite  noticeable  in  many  waters. 

The  sediment  may  be  earthy  or  fiocculent;  in  the  latter 
case  it  is  generally  debris  of  organic  matter  of  various  kinds. 
The  degree  of  turbidity  is  expressed  by  the  terms  "  very 
slight,"  "  slight,"  "  distinct,"  and  "  decided,"  and  the  degree 
of  sediment  by  "  very  slight."  "  slight,"  "  considerable,"  and 
"  heavy."  These  determinations,  again,  are  of  value  only  to 
the  routine  worker,  and  for  him  there  are  various  methods  in 
use.  The  papers  of  Parmelee  and  Ellms  '•=  and  of  Whipple 
and  Jackson  f  should  be  consulted  for  a  description  of  these. 

Determination  of  Alum. — On  account  of  the  use  of  alum 
or  aluminum  sulphate  as  a  coagulant  in  the  filtration  of  water, 
a  determination  of  alumina  in  the  effluent  water  is  often  nec- 
essary.   This  may  be  readily  made  by  the  logwood  test.t 

Directions. — Dissolve  about  o.i  gram  pure  haematoxylin 
in  25  c.c.  water;  this  solution  will  keep  for  two  weeks  and 
works  best  after  being  made  several  hours.  To  50  c.c.  of  the 
water,  placed  in  a  four-inch  porcelain  dish,  add  two  drops  of 
the  haematoxylin  solution,  allow  the  solution  to  stand  for 
one  or  two  minutes,  then  add  a  drop  of  20  per  cent,  acetic 
acid.  The  standards  are  prepared  at  the  same  time,  using 
50  c.c.  of  distilled  water  and  the  required  amount  of  a  stand- 

*  TecA.  Quart.,  12  (i8gg),  145.         f  Ibui.,  283. 
X  E.  H.  Richards:    Tech.  Quart.,  /^{iSgi),  194. 


Il8  AIR,    WATER,    AND    FOOD. 

arc!  alum  solution.  The  comparison  must  be  made  imme- 
diately, since  the  color  fades  on  standing.  In  this  way  the 
presence  of  one  part  of  aluminum  sulphate  in  five  million  can 
be  determined  directly  in  the  water  and  with  ease. 

Logwood  itself  can  be  used,  but  the  test  is  not  so  delicate 
as  with  the  hsematoxylin.  Boil  5  grams  rasped  logwood  re- 
peatedly with  50  c.c.  of  water;  reject  the  first  four  decoctions, 
saving  the  fifth  for  use.  This  solution  is  used  in  the  same 
way  as  the  hnematoxylin  solution,  but  the  [ainter  colors  are 
not  so  easily  seen,  on  account  of  the  greater  color  of  the  log- 
wood solution  itself.  The  logwood  solution  must  be  freshly 
prepared  each  time.  It  will  work  satisfactorily  only  for  about 
two  hours. 

Notes. — This  test  will  show  the  presence  of  all  soluble  salts 
of  aluminum  which  enter  into  combination  with  the  coloring 
matter  of  the  logwood  to  form  a  "  lake." 

The  alkalies  and  alkaline  earths  give  a  purplish  color  with 
logwood  extract,  hence  the  test  for  alum  can  be  made  only  in 
acid  solution. 

Determination  of  Lead. — Lead  in  the  minute  quantities 
in  which  it  ordinarily  occurs  in  water  is  best  estimated  by 
comparing  the  color  of  the  sulphide  with  standards. 

Directions. — If  the  water  is  colorless,  acidify  the  clear  solu- 
tion, concentrated  if  need  be,  with  two  or  three  drops  of 
acetic  acid,  and  pass  in  hydrogen  sulphide  to  saturation.  If 
a  color  is  produced,  compare  it  in  a  loo-c.c.  tube  with  the 
color  given  by  varying  quantities  of  a  standard  lead  solution. 

If  the  water  is  too  highly  colored  to  estimate  the  lead  di- 
rectly, evaporate  three  or  four  liters  in  a  porcelain  dish  to 
about  25  c.c,  add  10  c.c.  of  ammonium  chloride  solution  and 
a  considerable  excess  of  strong  ammonia.  Then  add  hydro- 
een  sulphide  water  and  allow  the  dish  to  stand  some  hours. 
Eoil  the  contents  of  the  dish  for  a  few  moments  to  expel  the 


water:  analytical  methods.  119 

excess  of  hydrogen  sulphide,  and  filter.  The  precipitate  con- 
tains all  the  lead,  iron,  and  suspended  organic  matter,  also 
copper  and  zinc  if  present,  while  the  soluble  color  goes  into 
the  filtrate.  Wash  once  with  hot  water,  transfer  the  filter  to 
the  original  dish,  and  dissolve  the  sulphides  by  boiling  with 
dilute  nitric  acid  (i  part  acid,  sp.  gr.  1.2,  to  5  parts  water). 
Filter  and  w^ash;  evaporate  to  10-15  ^-c,  cool,  add  5  c.c.  con- 
centrated sulphuric  acid  and  evaporate  until  copious  fumes 
are  given  off.  Then,  if  the  original  water  contained  less  than 
0.25  part  iron  per  million,  add  acetic  acid  and  ammonia,  boil, 
filter,  and  read  the  amount  of  lead  in  the  alkaline  filtrate, 
making  the  standards  (page  iii)  also  alkaline  with  ammonia. 

If  the  water  contained  over  .25  part  iron,  wash  the  lead 
sulphate  into  a  beaker  with  alcohol  and  water,  and  let  it  set- 
tle overnight.  Filter,  wash  free  from  iron  with  50  per  cent, 
alcohol,  dissolve  the  precipitate  by  boiling  with  ammonium 
acetate,  filter,  and  determine  the  lead  as  above. 

Note. — If  more  than  .25  part  of  iron  is  present,  some  of 
the  lead  will  be  held  by  the  precipitated  ferric  hydroxide;  and 
if  25  parts  are  present,  all  of  the  lead  may  be  lost  in  this  way; 
hence  the  modification  of  the  method  in  the  presence  of  con- 
siderable quantities  of  iron.* 

When  copper  is  also  present  it  is  detected  by  the  blue 
color  given  to  the  ammoniacal  filtrate  from  the  iron  precipi- 
tation. 

Statement  of  Results — In  reporting  water  analyses  the 
results  are  best  expressed  in  milligrams  per  liter,  which  for 
the  majority  of  waters  is  equivalent  to  "  parts  per  million." 
Occasionally  it  may  be  desirable  to  express  the  results  in 
"  grains  per  gallon."  Parts  per  million  may  be  converted  into 
grains  per  U.  S.  gallon  by  multiplying  by  0.058.     For  con- 


*  Ann.  Rep.  State  Bd.  Health,  Mass.,  1898,  577. 


I20 


AIR,    WATER,    AND    FOOD. 


venience  the  results  should  be  arranged  in  tabular  form,  such 
an  arrangement  being  suggested  below: 

SANITARY    WATER-ANALYSIS. 
(Parts  per  1,000,000.) 


Date. 

Physical.                                1 

Residue  on  Evaporation. 

No. 

Color. 

Turb. 

Sed. 

Odor. 

Total. 

Loss. 

Fixed. 

Change 

Cold. 

Hot. 

Ignition. 

121 

3-9-'oo 

.50 
0.0 
0.0 

Dec. 

None 

Cons. 
None 

None 

F.  Veg. 
None 

425 

64.0 

9740.0 

12,5 

30.0 

(Slight 
i  black 

133 

Nitrogen  as 

No. 

Total 
Organic. 

Alb.  Ammonia. 

Free  Am. 

Nitrite. 

Nitrate. 

Ox. 

Total. 

Sol. 

Susp. 

121 

.598 

.306 
.014 
.032 

.170 

.136 

.056 
.000 
.560 

.003 
.000 
.003 

.220 
1.40 
1. 14 

4.83 

.41 

3-23 

123 

Hardness 

Chlorine. 

Iron. 

Biological  (per  c.c.) 

No. 

Bac. 

Plants. 

Diatoms. 

Cyano- 
phyceae. 

Algae. 

Animals. 

20.0 

23.0 

560.0 

1.8 

6.3 

1198.0 

I 

0 

0 

229 

.01 

.46 

"3 

No.  121  is  from  a  pond;  122  from  a  spring;  123  from  an  artesian  well. 


CHAPTER    VIII. 

FOOD  IN  RELATION  TO  HUMAN  LIFE:   COMPOSITION,  SOURCES. 

DIETARIES. 

Paracelsus  (1493-1541)  taught  that  "the  object  of 
chemistry  is  not  to  niiike  gold,  but  to  prepare  medicines." 
Van  Helmont  (1577)  recognized  water  as  a  chief  constituent 
of  all  living  matter.  Sylvius  (1614)  taught  that  combustion 
and  respiration  were  precisely  similar  phenomena.  The  mod- 
ern revival  of  chemistry  has  been  largely  due  to  efforts  to 
preserve  health.  These  efiforts  are  turned  more  and  more  to 
the  attainment  of  a  high  degree  of  daily  efficiency  instead  of 
toward  curing  already  established  disease.  Life  itself  is  con- 
ditioned on  the  food-supply.  Wholesome  food  is  a  necessity 
for  productive  life.  Man  can  and  does  exist  on  very  unsuit- 
able, even  more  or  less  poisonous,  food,  but  it  is  merely  ex- 
istence and  not  effective  life.  This  is  true  not  only  of  the 
wage-earner,  but  of  the  business-man,  the  professional  man, 
the  scholar.  To  be  well,  to  be  able  to  do  a  day's  work,  is 
man's  birthright.  Nevertheless  a  too  large  proportion  of  the 
American  people  sells  this  most  valuable  possession  for  a 
mess  of  pottage  which  pleases  the  palate  for  three  minutes 
and  weights  the  digestive  organs  for  three  hours.  With  no 
other  known  source  of  bodily  energy,  the  student  cannot 
afford  to  use  up  the  capital  in  his  bank  lest  he  find  the  account 
overdrawn  before  middle  age.  With  no  hope  of  entirely  ban- 
ishing evil  microbes  from  the  haunts  of  men,  it  behooves  each 
one  to  so  nourish  his  body  that  the  enemy  can  find  no  point 
of  attack. 


122  AIR,    WATER,    AND    FOOD. 

The  watchword  of  the  State  is  prevention  of  disease;  that 
of  the  individual  is  personal  resistance.  The  economic  and 
social  conditions  of  daily  life  have  reached  such  a  stage  of 
development  as  to  make  a  closer  study  of  food-materials,  for 
which  half  the  cost  of  living  is  spent,  not  only  desirable  but 
imperative.  With  the  products  of  the  world  exposed  in  our 
markets,  the  restraints  of  a  restricted  choice,  as  well  as  in- 
herited instincts  or  traditions,  lose  their  force.  The  buyer, 
unless  he  has  actual  knowledge  to  guide  him,  is  swayed  by 
the  caprices  of  the  moment  or  the  condition  of  his  purse,  and 
often  fails  to  secure  adequate  return  in  nutritive  value  for  the 
money  paid. 

The  fact  that  so  much  manipulated  material  is  put  upon 
the  market  renders  this  choice  of  food  doubly  dif^cult,  since 
the  appearance  of  the  original  article  is  often  entirely  lost, 
and  to  city-bred  buyers  even  the  natural  product  conveys 
Httle  idea  of  its  money  value.  It  therefore  seems  necessary  that 
an  elementary  knowledge  of  the  proximate  composition  and 
food  value  of  the  more  common  edible  substances  should  be 
recognized  as  an  essential  part  of  education.  Chemistry  is 
now  found  in  the  curricula  of  nearly  all  institutions  devoted  to 
higher  education,  so  that  it  is  possible,  as  it  was  not  ten  or 
twenty  years  since,  to  bring  to  students  both  the  theoretical 
and  the  practical  bearing  of  a  study  of  food-materials  in  an 
instructive  and  practical  manner.  No  branch  of  Sanitary 
Chemistry  can  yield  more  far-reaching  results  in  the  welfare 
of  the  community,  since  the  more  widely  this  knowledge  of 
the  composition  of  foodstuffs  is  disseminated  the  less  danger 
to  health  and  purse  from  the  sophistications  of  unscrupulous 
dealers. 

True,  the  subject  is  not  yet  in  that  condition  in  which 
there  is  nothing  more  to  learn.  It  cannot  be  taught  in  a 
dogmatic  manner.      No   hard-and-fast   rules   can   be   given 


FOOD    IN    RELATION   TO    HUMAN    LIFE.  12$ 

■either  as  to  the  quantity  or  the  quahty  of  the  daily  diet,  but 
enough  is  known  to  enable  us  to  make  life  of  more  value,  to 
lessen  the  suffering  due  to  disease,  and,  consequently,  to 
lower  the  death-rate  and  increase  the  productive  power  of  the 
community. 

Attention  must  be  called  to  this  relation  of  food  to  health 
if  the  dehcacy  of  constitution  due  to  civilized  habits  is  to  be 
overcome  and  the  lives  of  useful  citizens  prolonged.  Men 
otherwise  sane  are  most  reckless  where  food  is  concerned. 
Even  noted  authorities  on  sanitation  have  succumbed  to  dis- 
ease because  the  proper  balance  of  nutrition  and  exercise 
was  neglected.  The  physician  is  to  a  great  extent  powerless, 
for  if  his  advice  displeases  he  is  dismissed.  It  remains  for 
the  school  to  educate  the  young  student,  and  as  usual  the 
higher  education  must  begin  the  work  and  the  college  pro- 
fessor must  set  the  example  of  a  living  plain  enough  to  be 
consistent  with  clear  thinking.  There  need  be  no  apology, 
therefore,  for  the  introduction  of  such  a  ''  practical  "  subject 
into  any  college  curriculum.  There  is  plenty  of  theory  be- 
hind it  and  much  educational  value  in  both  methods  and  rea- 
soning. 

Definition  of  Food. — Food  is  that  which  builds  up  the  body 
and  furnishes  energy  for  its  activities:  that  which  brings 
within  reach  of  the  living  cells  which  form  the  tissues  the  ele- 
ments which  they  need  for  life  and  growth.  Only  such  avail- 
able substances  can  be  called  food,  no  matter  what  their 
chemical  composition  may  be.  Soft  coal  contains  carbon  and 
hydrogen  and  is  food  for  the  furnace,  but  is  not  available  for 
the  animal  body. 

If  for  any  reason  a  portion  of  the  digestive  tract  is  dis- 
eased, substances  which  under  normal  conditions  would  be 
food  may  not  be  nutritious. 

The  nutritive  value  of  a  food  depends  upon  the  quantity  of 


124  AI^'    WATER,    AND    FOOD. 

its  ingredients  which  under  normal  conditions  may  be  useful 
to  the  human  organism.  The  term  is  not  confined  to  any- 
one class  oj  food  principles,  as  is  commonly  the  case  in  news- 
paper articles,  in  which  it  is  often  stated,  for  example,  that 
white  flour  and  rice  have  very  little  nutritive  value. 

We  determine  what  chemical  elements  enter  into  the 
composition  of  the  body  by  an  analysis  of  the  various  organs 
and  tissues.  We  learn  what  combinations  of  these  ele- 
ments serve  as  food  by  determining  those  present  in  mother's 
milk  and  in  foodstuffs  which  experience  has  proved  to  fur- 
nish perfect  nutrition.  From  these  studies  it  is  apparent  that 
about  fifteen  chemical  elements  are  constant  constituents  of 
the  human  body;  that  about  a  thousand  natural  products  are 
known  to  have  food  value;  that  of  these,  one  hundred  are  of 
world-wide  importance  (see  table,  page  130),  and  that  ten  of 
them  form  nine-tenths  of  the  food  of  the  world. 

Food  Principles. — While  the  foodstuffs  present  great  vari- 
ety, the  food  principles  may  be  grouped  under  four  headings; 
viz.,  nitrogenous  substances  or  proteids,  fats,  carbohydrates, 
and  mineral  salts.  Each  group  contains  many  members  with 
minor  but  often  essential  differences.  To  make  these  sub- 
stances available,  there  is  needed  an  ample  supply  of  air  and 
of  water, — of  water  for  solution  and  circulation,  of  air  for  the 
oxygen  needed  to  liberate  the  stored  energy  of  the  food  in  the 
place  where  it  will  accomplish  its  purpose. 

Nitrogenous  Substances. — Since,  in  some  w^ay  as  yet  un- 
known to  us,  nitrogen  is  essential  to  living  matter,  such  sub- 
stances as  contain  this  element  in  an  available  form  are  of  the 
first  importance.  Some,  as  albumen,  are  so  closely  allied  to 
human  protoplasm  that  probably  they  need  only  to  be  dis- 
solved to  be  at  once  assimilated.  Others,  as  gluten  and  sim- 
ilar vegetable  products,  undergo  a  greater  change;  while  still 
others,  as  gelatine,  have  a  less  profound  but  marked  effect  in 


FOOD    IN    RELATION   TO    HUMAN    LIFE.  12$ 

protecting  the  tissues  from  waste.  Still  other  nitrogenous 
substances,  as  the  alkaloids,  seem  to  affect  the  ;/£';x'(7-tissues 
for  good  or  ill. 

The  enzymes,  "  ferments,"  in  part,  of  the  older  nomencla- 
ture, are  also  highly  nitrogenous  substances  present  in  some 
form  in  nearly  all  foodstuffs  of  natural  origin.  The  nearer 
the  composition  of  the  food  approaches  that  of  the  protoplas- 
mic proteid,  presumably  the  greater  its  food  value,  since  each 
cleavage,  each  hydrolysis,  each  step  in  the  breaking  down  of 
the  highly  complex  molecule,  consisting  of  hundreds  of  atoms, 
is  supposed  to  liberate  the  stored  energy.  Therefore  it  is  not  a 
matter  of  indifference  in  what  form  this  essential  is  taken.  So 
little  is  known,  however,  with  scientific  accuracy  that  stu- 
dents will  find  a  fruitful  field  of  research  along  these  lines  of 
investigation.  Also  together  with  this  element,  nitrogen,  go 
others,  in  small  quantity  to  be  sure,  but  evidently  of  great 
value.  Such  are  sulphur,  iron,  phosphorus.  One  difference 
between  the  several  groups  of  proteids  is  seen  in  this  com- 
bination with  the  metallic  elements  which  seems  to  carry  with 
it  certain  effects.  Until  greater  progress  has  been  made  in 
determining  the  availability  in  the  organism  of  the  various 
known  substances,  we  must  be  content  with  a  wide  margin 
in  the  calculated  quantities  necessary  for  the  daily  efffciency, 
except  in  the  very  few  instances  of  nearly  pure  substances,  as 
white  of  egg.  It  is  evident  also  that  the  manner  of  prepara- 
tion and  the  kind  of  mixtures  used  in  food  will  affect  most 
profoundly  so  unstable  and  complex  a  class  of  substances, 
and  that  only  very  general  conclusions  can  be  drawn  from  the 
work  done  as  yet.  One  thing  is  certain,  that  the  body  cannot 
take  nitrogen  from  that  which  does  not  contain  it.  There- 
fore a  certain  quantity  of  highly  nitrogenous  food  should  form 
a  portion  of  the  daily  supply.  It  is  usually  held  that  the  body 
seems  to  be  sufficiently  nourished  when  the  food  contains 


126  AIR,    WATER,    AND    FOOD. 

an  amount  of  digestible  proteid  equivalent  to  about  loo 
grams  of  dry  albumen  per  day  for  the  average  adult,  although 
recent  work  has  shown  that  this  figure  is  probably  too  high. 
An  excess  appears  to  have  a  stimulating  etTect  and  overloads 
the  system  with  the  waste,  since  the  end-products  are  not 
purely  mineralized  substances,  as  are  carbon  dioxide  and 
water  from  the  carbohydrates,  but  are  compounds  of  an  or- 
ganic nature,  as  creatin,  urea,  and  uric  acid,  which  have 
deleterious  effects  when  accumulated  in  the  system.  A  de- 
ficiency of  nitrogen  is  made  good,  to  a  limited  extent,  by  the 
protective  agency  of  the  other  foodstuffs  which  offer  them- 
selves for  all  the  offices  except  the  final  one  of  tissue-building. 
Fats. — For  this  protective  action,  as  well  as  for  many  other 
purposes,  the  fats  are  most  valuable,  and  if  they  occur  in  about 
the  same  proportion  as  do  the  nitrogenous  elements,  the 
needs  of  the  organism  seem  to  be  well  met.  Thus,  in  mother's 
milk,  in  eggs,  and  in  meat  from  active  animals  these  two  are 
in  nearly  equal  proportions,  while  in  the  cereals  the  fat  is  less; 
in  nuts  and  in  meat  from  fattened  animals,  as  a  rule,  it  is 
higher  than  the  nitrogen.  Little  is  known  as  to  the  varying 
food  value  of  these  fats  from  different  sources.  Certain 
physical  conditions  of  solidity,  melting-point,  etc.,  seem  to 
have  more  influence  than  mere  chemical  composition.  What- 
ever the  source,  it  is  certain  that  the  stored-up  energy  which 
is  to  serve  the  organism  in  cases  of  loss  of  income  from  any 
cause  is  in  the  form  of  fat,  a  form  which  is  not  subject  to  the 
action  of  agents  which  so  readily  decompose  proteids  and 
carbohydrates  and  yet  is  readily  converted  into  available  food 
whenever  called  for.  That  it  is  not  absolutely  necessary  that 
the  food  should  contain  fat  as  such  seems  to  be  proved  by 
experiment,  but  from  the  fact  that  all  nearly  natural  food- 
substances  do  contain  it,  and  that  it  appears  to  be  more 
economical  of  human  energy  to  take  it  from  these  foods  than 


FOOD    IN    RELATION    TO    HUMAN   LIFE.  12/ 

to  manufacture  it  from  the  proteids  and  carbohydrates,  we 
may  safely  assume  fat  to  be  an  essential  of  the  human  dietary. 

That  the  equality  in  amomit  of  fat  with  nitrogenous  com- 
pounds is  not  essential  is  proved  by  the  fact  that  the  strong 
draft  animals,  as  horses  and  oxen,  take  food  in  which  the  per 
cent,  of  fat  is  not  more  than  half  as  much  as  of  proteid;  never- 
theless it  is  present  in  the  food  of  all  animals  and  doubtless, 
in  its  turn,  is  protected  by  an  excess  of  the  third  class  of 
foodstuffs,  the  carbohydrates,  characteristic  of  the  vegetable 
kingdom — a  class  which  in  the  final  decomposition  yield  clean 
volatile  products,  water  and  carbon  dioxide,  and  which,  there- 
fore, do  not  clog  the  system  ro  readily  as  do  urea  and  other 
wastes. 

Carbohydrates. — The  number  of  more  or  less  well-defined 
substances  under  this  head  is  legion:  starches  from  scores 
of  plants,  sugars  from  as  many  more,  gums,  pectins,  and 
dextrins,  all  with  a  certain  food  value,  dependent  prob- 
ably upon  the  utilization  of  the  various  mixtures  with 
w^hich  they  are  taken  into  the  alimentary  canal.  These 
foodstuffs  are  very  liable  to  "  fermentation,"  that  is,  to  an 
acid  decomposition  which  prevents  their  absorption  by 
the  delicate  lining  of  the  walls  of  the  intestines  and  which 
causes  digestive  disturbance.  The  sugars,  which  are  very 
soluble,  and  therefore  liable  to  be  present  in  excess,  are  es- 
pecially subject  to  this  change.  This  class  of  food-substances 
is  found  in  the  diet  of  civilized  man,  free  to  choose,  in  an 
amount  about  equal  to  the  sum  of  the  other  two  classes,  with 
a  tendency  to  less  rather  than  more.  It  may  be  said  that 
sugar  and  fat  increase  over  starch  in  the  diet  of  a  people  of 
unrestricted  choice,  but  it  is  not  certain  that  the  qualities  of 
body  which  make  for  hardihood  and  resistance  to  disease 
are  correspondingly  increased.  There  is,  indeed,  much  evi- 
dence to  show  that  power  of  digesting  vegetable  foods  indi- 
cates a  general  wcll-l^eing  of  body  conducive  to  long  life.    A 


128  AIR,    WATER,    AND   FOOD. 

ready  adaptation  renders  possible  the  changes  of  habitat  re- 
quired by  civiHzation.  Unless  one  is  to  be  confined  to  a  nar- 
row range  it  is  wise  to  cultivate  a  strength  of  digestion  as 
well  as  a  strength  of  muscle,  and  for  the  best  brain  power  we 
believe  it  to  be  more  essential. 

Mineral  Salts. — The  fourth  class,  mineral  salts,  comes  into 
the  food  largely  from  the  vegetable  substances  eaten,  for  in 
these  the  union  is  an  organic  one  readily  assimilated.  As  we 
have  seen,  certain  elements  go  with  the  nitrogenous  portion, 
as,  for  example,  in  gluten  and  its  congeners  are  found  sul- 
phur and  phosphorus.  Potassium,  found  in  barley,  is  a  con- 
stant constituent  of  protoplasm,  while  sodium  is  found  in 
blood-serum.  A  lack  of  vegetable  foods  seems  to  impoverish 
the  blood-corpuscles.  For  children,  a  deficiency  in  lime 
causes  serious  disease.  Sugar,  olive-oil,  corn-starch,  and 
other  prepared  food-substances  cannot  take  the  place  of 
asparagus,  cabbage,  carrots,  etc. 

Heat  of  Combustion. — Until  a  more  definite  knowledge 
of  the  processes  of  metabolism  (the  transformations  of  matter 
and  energy  in  the  animal  organism)  is  obtained  the  potential 
energy  of  food  is  calculated  in  terms  of  mechanical  work — 
expressed  in  heat-units  or  calories. 

One  Calorie  (looo  calories)  is  that  amount  of  heat  which 
is  required  to  raise  the  temperature  of  one  kilogram  of  water 
one  degree  centigrade,  and  if  expressed  in  terms  of  mechani- 
cal work  would  enable  one  ton  to  be  lifted  1.53  feet.  For 
example:  one  gram  of  fat  burned  under  a  steam-boiler  would 
yield,  if  the  heat  were  completely  utilized,  9.3  Calories,  and 
raise  one  ton  14.2  feet;  100  grams  would  yield  930  Calories 
and  raise  one  ton  1423  feet. 

One  gram  of  proteid  or  of  carbohydrate  is  usually 
reckoned  as  yielding  only  4.1  Calories.  480  grams  would 
yield  1968  Calories  and  raise  one  ton  301 1  feet.  A  day's 
ration  is  frequently  estimated  as  100  grams  fat  -f  480  grams 


FOOD    IN    RELATION    TO    HUMAN    LIFE.  1 29 

of  proteid  and  carbohydrates,  and  if  completely  converted 
into  mechanical  work- would  yield  that  amount  of  energy 
which  would  suffice  to  raise  156  pounds  (taken  as  the  weight 
of  the  average  human  body)  56,755  feet.  But  a  portion  of 
this  energy  is  used  up  in  chemical  processes,  a  portion  in 
physical  changes,  and  a  portion  is  undoubtedly  wasted;  a 
portion  of  the  food  may  be  of  no  use  or  even  detrimental  to 
the  body,  so  that  not  more  than  one-third  of  this  work  can 
be  counted  as  available.  Hence  18,918  feet  may  be  counted 
as  a  theoretical  day's  work  in  mountain-climbing. 

The  fact  remains,  however,  that  all  experiments  yet  made 
go  to  show  that  within  practical  limits  we  are  safe  in  using 
the  heat  of  combustion  (expressed  in  Calories)  of  any  food- 
substance  as  a  controlling  measure  of  food  values.  The  re- 
quisite number  of  Calories  must,  however,  be  obtained  by 
the  utilization  of  such  substances  as  contain  all  the  elements 
needed  by  the  body,  and  in  such  ratio  as  has  been  found  avail- 
able for  the  balance  of  nutrition.  In  carrying  on  its  multi- 
farious activities  the  body  loses  about  20  grams  of  nitrogen 
per  day,  which  must  be  replaced  by  the  same  element  in  the 
food  taken.  Thus  while  the  requisite  number  of  Calories  may 
be  furnished  by  fat  or  starch,  these  substances  alone  will  not 
suffice  for  complete  nutrition.  The  nutritive  ratio,  or  the 
proportion  of  nitrogenous  to  non-nitrogenous  food,  must  be 
maintained  in  the  proportion  of  i  to  3,  or  at  least  i  to  5. 

The  following  table  of  one  hundred  common  food-mate- 
rials is  arranged  in  the  order  of  calorific  or  energy-giving 
power,  but  in  considering  the  food  value  of  any  one  substance 
its  nitrogen  content  must  also  be  considered,  and  such  com- 
binations made  as  will  yield  the  requisite  elements  for  a  well- 
balanced  ration. 

From  even  a  cursory  examination  of  the  table  it  will  be 
seen  how  widely  some  of  the  foodstuffs  differ  under  differing 
conditions  of  soil  moisture,  fertilization  in  the  case  of  plants. 


I30 


AIR,    WATER,    AND    FOOD. 


COMPOSITION    OF    SOME    COMMON    FOOD-MATERIALS    AS    PURCHASED, 

I.  Fuel  Value  3000-4000  Calories  per  Pound. 


Food-material. 


Butter I 

Lard  (refined) 

Oleomargarine. . . . 

Salt  fat  pork 

Suet 

Walnuts  (shelled) 


Refuse. 


Per  cent. 


Water. 


Per  cent. 
II  .o 


9-5 
0.3  to  12.2 
4.3  to  21  9 

2-5 


Nitroge- 
nous 
Substances. 


Per  cent. 


0.2  to  5.0 
I.I  to  7.5 

16.6 


Per  cent. 

85.0 

ICX5.00 

83.0 

80.3  to  94.1 
70.7  to  94.5 

63.4 


Carbo- 
hydrates. 


Per  cent. 


II.  Fuel  Value  2000-3000  Calories  per  Pound. 


Bacon     

Cheese  (American  pale). 

Chocolate 

Doughnuts 

Mutton  tiank  (fat) 

Peanut  butter 

Sausage  (farmer). 


18.4 

31.6 
1.5  to  10.3 
II. o  to  25.8 

28.9 
2. 1 


9-5 

59-4 

28.8 

35-9 

0.3 

2.5  to  13.4 

47.1  to  50.2 

26.8  to  33.8 

5.1  to  7.6 

16.4  to  25.7 

45.8  to  63.2 

10.7 
293 

59-8 
46. s 

17. 1 

27.9 

40.4 

III.  Fuel  Value  1500-2000  Calories  per  Pound. 


Barley  (pearled) 

Beans  (dried) 

Cake  average  (except  fruit)  — 

Candy 

Cheese  (Neuchatel) 

Corn-meal 

Corn-starch   . 

Crackers  (average) 

Fat  meats 

Gelatin 

Ham  (smoked,  medium  fat)   .. 
Infants'  and  invalids'  foods . . . 

Macaroni 

Oats 


Peanuts 

Peas  (dried) 

Popcorn.   

Rice   

Rye  flour 

Sugar  (granulated) 

Wheat  (entire)  flour 

W'heat  flour  (white  bakers'). 

Wheat  (shredded) 

Zwieback 


II. 7 


4.5  to  28.4 


9.8  to  ia.9 
9.6  to  15.5 

19.9 
4.0 

42.7  to  57.2 

8.8  to  17.9 
10. o 

6.8 

38.3 

13-6 
27.3  to  42.5 
2.4  to  12.3 

7.0  to  12.3 

7.8 

6-9 

6.9  to  15.0 

4-3 

9.1  to  14.0 
II. 9  to  136 


7.0  to  10. 1 
19.9  to  26.6 

6.3 


15. 1  to  22.3 
6.7  to  11.6 


6.4  to  13. 1 
10. 1  to  13.3 
7.2  to  10.7 
5.0  to    7.7 

Including  fibre. 


10.7 

13.0 

84.2 
10.2  to  2i.g 
2.0  to  22.5 
7.9  to  16.6 

16. 5 

19.5 
20.4  to  28.0 

10  7 

5.9    to  II. 3 

4.9  to    8.8 


12.2  to  14.6 

10.3  to  14.9 

9.6  to  II. 4 

8.6  to  II. 7 


0.7  to  1.5  I77.3  to  78.1* 
1.4  to  3.1  57.2  to  63.5* 
9.0  63  3 

96.0 
0.2  to  2.9 
)8.4  to  80.6* 
90  o* 
71.9* 


22.3  to  32.5 
I  .0  to  5.3 


8.8 

36. S 

0.1 

24.5  to  39.9 

0.3  to  10.9 

0.0  to    4.9 

7-3 

29.1 

0.8  to  1.3 

50 

O.I   to  0.7 

0.2  to  1.3 


I.S    to    2 

1.9  to  2.0 
1.3  to  1.6 
8.1  to  1 1. 3 


66.9  to  89.4 

67.2  to  78.4* 
66.5* 
18.5 

58.0  to  67.4'" 

78.7 

75.4  to  81.9* 
77.6  to  80.2* 

100 

69.5  to  77.0* 

70.3  to  75.5 
75.0  to  79.7* 

72.1  to  74.2 


IV.  Fuel  Value  1000-1500  Calories  per  Pound. 


Apples  (dried) 

Bread  (white) 

Corn-bread 

Dates 

Figs  

Fresh  pork  (ribs  and  shoulder). 
Medium  fat  mutton  and  beef.., 

Mince-meat  (commercial) 

Mince-meat  (home-made) 

Pies 

Prunes  (dried) 

Raisins 

Sandwiches 

Sardines  (canned) 

Salt  mackerel 


15.9  to  20.3 
14.4  to  27.8 


150 

lO.O 


5.0 

22.9 


8.6  to  47.4 

35-3 
28.4  to  48.0 

13.8 
1 1.6  to  25.0 
40.1  to  43.6 
38.0  to  44.9 

27.7 

54-4 
44.9 
19.0 
13.1 
44.9 
53.6 
32-5 


48.6  to  86.91 

53-1 
40.3  1054.3 

70.6 
68.3  to  83.1 


60.2 
32.1 
39-2 
62.2 
68.5 
33-3 


FOOD    IN    RELATION    TO    HUMAN    LIFE. 


131 


COMPOSITION    OF    SOME    COMMON    FOOD    MATERIALS. —  Continued. 

V.  Fuel  Value  500-1000  Calories  per  Pound. 


Food-material. 


Refuse. 


Niirog-e- 

nous 

Substances. 


Carbo- 
hydrates. 


Beef  (round)   

Beef  (sirloin  steak). 
Chicken  (fowls) . . . . 

Cream  

Eggs 

Herring  (smoked) . . 

Meats  (lean) 

Olives  

S.ilmon  (fresh). ..  . 
Salmon  (canned)... 
Tapioca  pudding. . , 

Tongue  (beef) 

Turkey 

Veal  (breast) 


Per  cent. 

8.5 

12.8 

18.0  to  42.7 


44.4 
0.5  to  11.3 

19.0 
23.8  to  35.. 
II. 7  to  16  9 


9.2  to  553 
17.1  to  32.4 
15.7  to  25.4 


Per  cent. 

62.5 
54.0 

38.3  to  53.7 
74.0 

65-5 

19.2 

59.9  to  69.2 

52.4 
45.0  to  51 
54.6  to  58, 

52.0  to  71 

32.4  to  69 

41. 1  to  44. 

48.5  to  55. 


Per  cent. 
ig.2 
16.5 

11. 5  to  16.0 
2.5 

11.9 
20.5 

18. 1  to  21.4 

1.4 

12.6  to  15.0 

1S.6  to  20.2 

2.8  to  4.2 
7.8  to  20.2 
15.8  to  16.8 

14.2  to  16.9 


Per  cent. 
9.2 
16. 1 
6.9  to  21.5 
18.5 
9-3 
8.8 

7.8  to  14.2 
21 .0 

6.6  to  9.5 
5.6  to  9.8 

2.3  to  4.8 
0.7  to  15.3 

5.9  to  25.5 

9.4  to  12.8 


VI.  Fuel  Value  400-500  Calories  per  Pound. 


Beans  (canned  red  kidney). 

Calf  "s-foot  jelly  

Salt  cod  (boneless) 

Succotash  (canned) 

Sweet  potatoes 


72.7 

77.6 

54.8 

71.4  to  79.9 


277 
.9  to 


0-3 
to  I 
0.6 


VII.  Fuel  Value  300-400  Calories  per   Pound. 


Bananas.  ..  . 
Butter  beans. 
Fish  (fresh)  . 

Grapes 

Hash 

Milk 

Potatoes 


50.0 

25.2  to  46.0 

25.0 


4S.9 

0.8 

29.4 

4-7 

I  to  49.1 

II. 9  to  12.0 

58.0 

I.O 

80.3 

6.0 

87.0 

3-3 

62.6 

1.8 

0.4 

0-3 
1.8  to  5.9 
1.2 
1.9 
4.0 


VIII.  Fuel  Value  200-300  Calories  per  Pound. 


Apples 

Chicken  (broilers). 

Cranberries 

Onions 

Oysters  (solid) 

Parsnips 

Pears 


25.0 
31.4  to  55.1 


20.0 
10. o 


63.3 
44.6  to  52.4 
87.6  to  89.5 

78.9 

82.2  to  92.4 

66.4 

76.0 


9.0  to  15.7 

0.4  to  0.5 

1.4 

4.5  to  7.3 
1-3 
0.5 


0.3 
I.I  to  1.8 
0.4  to  0.9 

°-3 

o.s  to  1.8 

0.4 

0.4 


IX.  Fuel  Value  100-200  Calories  per  Pound. 


Beets 

Cabbage 

Carrots ...  . 

Gf  een  corn 

Lemons 

Oranges 

Soups  (canned) 

Spinach.. 

Squash 

Tomatoes  (canned). 


20.0 
15.0 

20.0 
61.0 
30.0 
27.0 


77 
70 
29, 
62 

63 

91.0  to  92.8 
91.6  to  92.8 

44  2 
92.5  to  97.9 


'•3 

1.4 
0.9 


2.q  to  5.0 
1.8  to  2.4 

o  7 
0.3  to  1.7 


0.2 
0.4 
o.s 

O.  I 
0.2    to   0.8 

0.2  to  0.5 

0.2 

0.1  to  0.3 


X.  Fuel  Value  10-100  Calories  per  Pound. 


Asparagus 

Bouillon  (canned) 
Celery 
Cucumbers 
Watermelons 


1.8 
1.7   to  2,6 

0.9 


Per  cent. 


21.9  to  38.1 


i».5 
17  4 


14.9  to  23.4 
21.9 


J4-3 
14.6 


14.4 
9.4 

14.7 


10.8 


9.3  to  10.9 

8.9 

1. 5  to  6,2 
10.8 
12.7 


7-7 
4.8 

7-4 

7-7 

S-9 

8.5 
0.6  to  5.7 
3.1  to  3.4 

4-5 
1.4  to  8.1 


3-3 
.1  to  0.3 

2.6 
2.6 
2-7 


132 


AIR,    WATER,    AND    FOOD. 


and  of  fatness  or  leanness  in  animals,  of  method  of  prepara- 
tion or  of  combination  in  cooked  foods. 

Therefore  examinations  of  materials  are  imperative  if 
there  is  to  be  any  basis  of  calculation.  In  an  institution  where, 
for  instance,  flour  forms  two-thirds  of  the  daily  ration,  if  it 
contains  the  lowest  per  cent,  of  nitrogen  it  may  not  furnish 
sufficient  proteid  for  a  well-balanced  ration,  or  if  the  meat 
used  is  very  lean  there  may  not  be  fat  enough  for  the  best  nu- 
trition. 

The  great  variation  in  the  proportion  of  water  leads  to 
many  surprises,  and  the  amount  of  unedible  material  is  to  be 
considered.  The  uneducated  provider  buys  oysters  under  the 
impression  that  he  is  furnishing  food  of  high  value,  and  does 
not  distinguish  between  potatoes  and  rice. 

In  the  present  state  of  our  knowledge,  the  best  use  to 
which  we  can  put  such  tables  and  analyses  is  as  a  check 
against  gross  errors  of  diet,  which  are  found  with  alarming 
frequency  especially  among  children  and  students,  those  who 
can* least  afford  to  make  them.  References  will  be  found  in 
the  Bibliography  to  works  for  further  study  along  these  lines. 

Dietaries. — A  dietary  is  simply  a  known  amount  of  food  of 
known  composition  per  person  per  day,  week,  or  month. 

What  is  called  a  standard  dietary  is  such  a  combination  of 
food-materials  as  shall  furnish  the  amounts  held  to  be  neces- 
sary.   The  following  are  examples  of  such  standard  dietaries: 


Approximate  Amounts 
required  daily  by 

Nitroorenous, 
grams. 

Fats, 
grams. 

Carbohydrates, 
grams. 

Calories. 

Child  of  6-9 

62 

73 
100 
100 
125 

45 

45 
75 

QO 
125 

200 
281 
380 
450 
500 

1593 

Child  of  Q   14 

1890 

2665 

Adult  at  moderate  work 
Adult  at  hard  work. . . 

3092 
3725 

(In  feeding  experiments  from   10  to  20  per  cent,  more   must  be  allowed 
for  waste  and  indigestibility.) 


FOOD   IN   RELATION    TO    HUMAN    LIFE.  1 33 

From  the  table  on  p.  130  may  be  selected  such  food  as  will 
give  the  required  quantities  in  variety  enough  to  suit  any  taste. 
That  which  the  table  cannot  give  is  the  percent,  of  each  which, 
under  any  given  condition,  will  be  utilized  by  the  person  fed. 
The  strength  of  the  digestive  juices,  exercise,  fresh  air,  the 
cooking,  the  mixing  of  the  foods,  the  habits  of  mind  as  to 
food,  the  customs  of  the  family,  all  influence  this  utilization, 
so  that  other  means  must  be  resorted  to  in  order  to  gain  an 
idea  of  what  is  practicable.  This  is  done  by  taking  account 
of  the  food  of  persons  free  to  choose  ;  of  those  in  different 
countries,  in  difTerent  circumstances,  and  using  a  great 
variety  of  materials.  Since  Voit  made  his  standard  dietary  in 
1870,  many  hundreds,  at  least,  have  been  so  gathered  in  the 
United  States  alone — more  than  two  hundred  since  1886.  All 
the  information  thus  gained  goes  to  confirm  the  theoretical 
standard,  and  also  to  show  how  much  depends  upon  suitable 
preparation  and  combination.  These  last  two  things  help 
each  other. 

As  food  is  ordinarily  prepared,  about  10  per  cent,  must 
be  deducted  for  indigestibility  in  a  customary  mixed  diet,  and 
about  10  per  cent,  more  for  the  refuse  or  waste  of  food  as 
purchased,  so  that  of  the  total  pounds  of  meat,  vegetables, 
and  groceries  some  20  per  cent,  is  of  no  final  service  in  the 
body.  It  is  immaterial  whether  this  amount  is  subtracted 
from  the  final  calculation  or  whether  the  higher  figures  be 
taken,  that  is,  whether  125  grams  of  proteid  as  purchased  or 
TOO  grams  final  utility  is  used.  There  will  be  an  unknown 
limit  in  either  case.  According  to  late  experiments  100 
grams  of  proteid  is  high.  The  waste  of  fats  is  less  in  propor- 
tion as  the  dietary  is  a  restricted  one. 

Knozi'lcdge  of  Food  Values  Necessary. — The  most  serious 
aspect  of  the  food  question  is  that  the  taking  of  it  is  volun- 
tary, not,  like  air,  a  necessity  beyond  control,  and  that  the 


134  AIR,    WATER,    AND    FOOD. 

most  fantastic  ideas  are  allowed  to  rule.  The  day-laborer  is 
in  little  danger,  since  his  food  demand  is  made  strong  by  out- 
of-door  exercise;  but  the  student  who  shuts  himself  up  in 
hot,  close  rooms,  and  who  does  not  look  upon  food  as  his 
capital,  but  only  as  a  disagreeable  task  or  an  amusement,  is  in 
great  danger,  as  is  he  who,  having  heard  that  one  can  live  on 
a  few  cents  a  day,  proceeds  to  try  it  without  knowledge,  and 
suffers  a  loss  of  efficiency  for  years  or  for  all  his  life. 

It  is  not  nearly  so  difficult  to  acquire  a  working  knowl- 
edge of  food  values  as  of  whist  or  golf,  so  that  on  entering  a 
restaurant  a  suitable  menu  may  be  made  up  within  one's  al- 
lowance. It  is  only  necessary  to  correct  prevailing  impres- 
sions and  reinforce  one's  experience. 

Figs,  dates,  raisins,  and  prunes  are  apt  to  be  regarded  as 
luxuries  instead  of  as  rich  food-substances  of  a  most  di- 
gestible kind  when  freed  from  skin  and  seed.  Nuts  are  a 
much  neglected  form  of  wholesome  food,  admirably  suited 
to  a  winter  table  from  their  richness  in  fat,  and  also  furnish- 
ins:  muscular  energv,  as  is  seen  in  the  agile  squirrel,  and  is 
proved  by  many  human  examples.  With  nuts,  however, 
must  be  taken  fruits  or  other  bulky  foods,  to  balance  the  con- 
centration. The  somewhat  compact  and  oily  substance  must 
be  finely  divided  and  freed  from  its  astringent  skin. 

In  distinction  from  these  rich  foodstuffs,  we  find  oranges, 
apples,  etc.;  the  usual  garden  vegetables,  asparagus,  lettuce, 
etc.,  which,  while  they  fill  an  important  place  in  the  dietary, 
add  little  directly  to  the  energy  of  the  body  and  need  not  be 
considered  except  as,  by  their  flavor  or  aesthetic  stimulus, 
they  add  to  the  efficiency  of  the  rest. 

In  looking  over  some  housekeeping  bills  of  a  family  not 
given  to  extravagance,  but  with  a  well-stocked  market  at 
hand  and  no  especial  check  on  the  cook's  orders,  it  was  found 
that  the  ten  staple  articles  cost  50  per  cent,  of  the  whole,  the 


FOOD    IN    RELATION   TO    HUMAN   LIFE.  1 35 

really  nutritious  foods  of  higher  price  20  per  cent.,  and  the 
mere  accessories  30  per  cent. 

These  accessories  are  truly  cheaper  than  doctors'  bills,  and 
a  high  rate  of  efficiency  in  human  mechanics  is  worth  attain- 
ing even  at  a  considerable  expense.  The  chief  difficulty  lies 
in  a  subject  outside  the  scope  of  these  pages,  namely,  waste 
of  the  expensive  or  less  nutritive  material,  or  substitution  of 
these  for  others  more  nutritive.  For  instance,  a  meal  of 
lettuce  dressed  with  oil,  eaten  with  bread  and  cheese,  fulfils 
all  the  requirements  of  nutrition,  and  may  cost  five  cents.  The 
same  food  value  from  sweetbreads,  grape-fruit,  etc.,  might 
cost  a  dollar. 


CHAPTER  IX. 

THE   PROBLEM    OF    SAFE    FOOD.      ADULTERATION    AND 
SOPHISTICATION. 

Where  food-materials  are  abundant,  of  known  value,, 
and  without  foreign  admixture,  there  the  general  welfare  of 
the  people  is  satisfactory,  barring  sanitary  errors  in  other 
directions.  Where  opportunity  is  given  for  the  unscrupu- 
lous dealer  to  increase  his  gains  at  the  expense  of  the  health 
and  lives  of  the  people,  children  especially,  it  is  eagerly 
seized  upon,  and  milk  diluted  with  water,  colored  with  coal- 
tar  products,  and  preserved  with  borax  or  formaldehyde  is 
furnished  so  long  as  the  community  is  ignorant  enough  to 
permit  it. 

In  frontier  towns  baking-powder  containing  alum  is  still 
sold,  and  in  many  places  ginger  containing  50  per  cent,  of 
turmeric,  buckwheat,  and  redwood  sawdust  is  on  the  market. 

The  average  buyer  is  content  to  go  by  familiar  appear- 
ance, and  is  quite  satisfied  if  he  sees  a  dead  bee  in  his  honey 
and  the  usual  form  and  color  in  his  coffee-bean.  Scientific 
skepticism  has  not  yet  touched  the  purchaser  of  the  essentials 
of  life,  and  manufacturers  are  not  slow  to  perceive  and  to 
take  advantage  of  his  credulity.  It  is  not  necessary  to  resort 
to  poisonous  material  or  to  directly  deleterious  substances^ 
it  is  only  necessary  to  mix  a  cheaper  but  equally  wholesome 
material  with  a  favorite  article,  or  to  substitute  it  altogether. 

To  meet  the  craving  for  variety  it  is  only  necessary  to  make 

136 


THE  PROBLEM  OF  SAFE  FOOD.  137- 

slight  changes  in  the  outward  appearance  of  common  sub- 
stances and  then  to  advertise  widely  the  discovery  of  some 
new  process  by  which  the  food  value  is  increased  tenfold. 
In  order  that  the  community  may  be  supplied  with  safe  food, 
as  well  as  with  safe  water,  the  education  of  the  individual  is 
important,  even  essential,  since  food  is  even  more  completely 
under  individual  control  than  is  water.  It  is  true  that  State 
and  municipal  regulations  exist  and  should  be  enforced  as 
to  palpably  noxious  substances  and  those  that  are  notoriously 
fraudulent.  The  relation  of  the  citizen  to  these  is  the  same 
as  to  the  purity  of  the  water-supply;  it  is  his  duty  to  uphold 
the  hands  of  the  authorities  in  the  necessary  expense  of  in- 
spection and  prosecution. 

Adulteration  and  Sophistication. — To  adulterate  is  defined 
as  to  debase,  "  to  make  impure  by  an  admixture  of  baser 
materials,  as  in  the  case  of  coin,  liquors,"  etc. 

As  an  explanation  of  sophistication,  which  is  often  used 
as  synonymous  with  adulteration,  this  quotation  is  given: 
"  These  men  have  obscured  and  confounded  the  nature  of 
things  by  their  false  principles  and  wretched  sophistry." 
(South.) 

The  sophists  were  educated  and  intelligent  men,  and  per- 
suaded the  people  by  specious  reasoning.  The  modern 
"  pure  food  "  manufacturer  is  a  sophist  who,  with  great  skill 
and  by  the  aid  of  the  well-paid  expert,  persuades  the  general 
public  that  he  is  their  benefactor  in  that  his  chemists  have 
penetrated  nature's  secrets,  hidden  from  the  ordinary  man, 
and  therefore  that  he  is  able  to  ofTer  them  long  life  and  pros- 
perity at  so  many  cents  the  pound. 

Although  the  words  "  adulteration "  and  "  sophistica- 
tion "  are  in  a  degree  synonymous,  yet  there  is  a  distinction 
which  seems  borne  out  in  legal  practice.  To  adulterate  the 
coin  of  the  realm  or  the  liquor  of  the  bar  with  a  baser  metal 


138  AIR,    WATKR,    AND    FOOD. 

or  an  imitation  whisky  is  a  heinous  offence.  So  is  the  mix- 
ture of  milk  with  the  baser  article,  water,  which  thereby  low- 
ers its  food  value.  But  the  "  wretched  sophistry "  which 
obscures  the  nature  of  things  on  a  package  of  prepared  food 
misleads  more  persons  and  inflicts  more  injury  upon  the  com- 
munity than  the  other,  yet  goes  unrebuked.  The  most 
barefaced  assertions  are  printed  in  magazines,  and  "  pure- 
food  shows  "  only  whet  the  appetite  for  something  new. 

Prcdigcstcd  Foods. — This  craving  for  something  new  to 
stimulate  a  jaded  appetite  already  spoiled  by  endless  variety 
and  bad  combinations  has  led  to  the  manufacture  of  a  cereal 
preparation  for  nearly  every  day  in  the  year.  No  better  com- 
mentary on  the  laziness  or  wilful  ignorance  of  American  pro- 
viders could  be  made  than  this.  Little  do  the  people  know 
about  wheat  or  cooking  if  they  suppose  that  grain  can  be 
changed  by  manipulation  in  any  kind  of  machine  so  as  to  give 
greater  food  value  than  was  contained  in  the  grain.  While 
it  is  true  that  some  of  these  preparations  are  far  better  than 
the  half-cooked  grains  found  on  so  many  tables,  the  fact  re- 
mains that  it  is  the  cook  and  not  the  substance  which  is  poor. 
The  false  statements  on  food  packages  of  all  kinds  are  so 
absurd  that  they  would  defeat  their  own  purpose  were  they 
viewed  in  the  light  of  common  sense.  It  is  not  always  best  to 
have  food  which  is  too  easily  digested. 

"  The  excessive  fear  of  indigestible  food  which  prevails 
among  the  wealthier  classes  may  lead  to  universal  debility  of 
the  intestinal  muscular  walls."  *  This  fear  and  the  lack  of 
exercise  is  working  mischief  especially  among  students. 
Colleges  do  not  educate  along  the  fundamental  lines  of 
health.  To  be  sure,  gymnasiums  are  becoming  common, 
and  sometimes  exercise  does  correct  bad  habits  of  eating,  but 

*  Bunge:  "  Physiological  Chemistry"  (trans.),  1890,  83. 


THE    PROBLEM    OF    SAFE    FOOD.  1 39 

a  knowledge  of  food  principles  should  go  along  with  it  in 
order  that  the  greatest  efifiqency  may  be  obtained. 

A  predigested  food  is  quickly  absorbed  into  the  circula- 
tion, and  hence  a  small  quantity  causes  a  sensation  of  fulness 
and  satisfaction  which,  however,  soon  passes  away  and  a 
faintness  results.  This  is  especially  true  of  the  sugars  and 
dextrins.  Frequent  meals  should  go  with  these  easily  ab- 
sorbed foods.  This  rapid  digestion  is  the  cause  of  much 
pernicious  eating  of  sweets  between  meals,  which  satisfies 
the  appetite  for  the  time  being  and  prevents  substantial 
quantities  of  other  foods  being  taken  at  the  time  they  are 
offered. 

A  lack  of  responsibility  for  the  energy  which  we  owe  to 
the  world,  an  inconsiderateness  for  the  sufifering  we  bring 
upon  others,  leads  us  to  walk  upon  the  thin  ice  of  mere  whim- 
sical eating. 

Extent  of  Adulteration. — The  proportion  of  food  adul- 
terated in  the  sense  of  harmful  additions  has  always  been 
comparatively  small;  probably  in  no  community  has  it 
ever  reached  10  per  cent,  of  the  food  sold.  In  States 
which  have  legal  penalties  it  is  undoubtedly  below  5  per 
cent.  Such  statements  as  that  90  per  cent,  of  the  food 
offered  in  any  market  is  adulterated  can  only  mean,  if 
true  at  all,  that  90  per  cent,  of  all  the  names  of  materials 
sold  in  shops  cover  more  or  less  fraudulent  mixtures.  For 
instance,  flour  is  rarely  adulterated;  pepper,  ginger,  and 
mustard  are  nearly  always  heavily  "dulterated.  For  one 
pound  of  these  substances  sold,  1000  pounds,  or  more,  of 
flour  go  out  from  the  store.  Looked  at  in  this  lieht  the  sub- 
ject assumes  quite  another  aspect.  A  canvass  of  the  State 
of  Massachusetts  in  1879,*  before  the  passage  of  the  law  of 

*  Ellen    U.  Richards:   "The   Adulterations  of  some   Staple  Groceries." 
Ann.  Rep.  Mass.  State  Bd.  Health,  1879  (Supp.),  55. 


140  AIR,    WATER,    AND    FOOD. 

1882  and  subsequent  restrictions,  showed  that  the  staple  arti- 
cles were  very  little  adulterated;  that  then,  as  now,  it  was  the 
condiments,  of  which  only  a  small  quantity  is  used  at  any  one 
time,  which  showed  the  highest  per  cent. 

The  influence  of  a  stringent  law  fairly  well  enforced  is 
seen  in  the  decrease  of  the  adulteration  of  cream  of  tartar  in 
samples  examined,  which  fell  from  42  per  cent,  in  1879  to 
5  per  cent,  in  1898. 

Of  suspicious  samples  of  foods,  exclusive  of  milk,  exam- 
ined in  the  latter  year  by  the  State  of  Massachusetts,  only 
13.4  per  cent,  were  adulterated.  Since  only  suspected  arti- 
cles were  taken  by  the  inspectors,  the  actual  per  cent,  must 
be  far  below  this.  Estimated  on  the  total  quantity  sold,  it  is 
doubtful  if  more  than  one  per  cent,  of  food  which  can  come 
under  the  law  is  adulterated  in  Massachusetts  to-day.  The 
records  of  localities  without  the  legal  protection  of  inspec- 
tion is  not  quite  so  good  as  those  of  the  five  States  which  have 
stringent  laws,  and  yet  it  is  doubtful  if  harmful  adulteration  is 
very  prevalent. 

Trade  Names. — Much  of  this  so-called  adulteration  de- 
ceives only  the  ignorant  buyer.  *'  Strictly  pure  "  is  a  well- 
understood  trade  term  and  means  "  with  a  certain  per  cent, 
of  addition";  "pure"  has  a  greater  addition,  as  "pure" 
spices.  Of  patent  and  proprietary  preparations,  and  those 
covered  by  a  trade  name,  the  sale  is  on  the  increase,  so  that 
the  statement  is  justified  that  the  frauds  in  foodstuffs  are 
mainly  commercial,  and  not  harmful  in  a  direct  way.  Among 
the  most  serious  are  those  packages  claiming  to  consist  of 
gluten  and  to  furnish  a  substitute  for  hearty  food  and  those 
so  largely  used  by  students.  "  Gluten  flour  "  is  not  what  the 
uninstructed  might  think,  that  which  is  very  rich  in  gluten, 
but  is  only  a  whole  wheat,  possibly  a  very  little  richer  in 
nitrogen  than  ordinary  flour.     "  What's  in  a  name  "  is  well 


THE    PROBLEM    OF   SAFE    FOOD.  I4I 

understood  by  sardine-canners,  bread-makers,  restaurant- 
keepers,  and  grocers.  The  dealer  caters  to  the  people  and 
goes  no  farther  than  they  readily  follow  him. 

Special  Cases. — The  use  of  canned  goods  brings  certain 
dangers  in  the  dissolved  metals  from  the  cans  or  from  the 
solder,  also  from  a  careless  habit  of  allowing  food  to  stand 
in  the  opened  tins.  The  liking  for  bright  green  pickles  and 
peas  leads  to  coloration  by  copper  salts.  The  demand  for 
cheap  jellies  has  developed  a  new  industry.  The  parings  and 
cores  of  apples  prepared  for  drying  are  cooked,  strained,  col- 
ored, and  flavored  to  make  to  the  eye  a  fair  imitation  of  rasp- 
berry, currant,  and  grape  jelly,  sold  for  7  to  10  cents  a 
tumbler. 

Flavoring  extracts  offer  a  fertile  field  for  chemical  su'b- 
stitutes. 

The  excessive  use  of  preservatives  is  caused  by  the  crav- 
ing for  food  out  of  season  and  out  of  place:  for  summer  fruit 
in  winter,  for  oysters  a  thousand  miles  inland,  and  by  the 
urban  demand  for  fresh  milk,  which  must  be  brought  at 
least  one  hundred  miles  and  can  be  delivered  but  rarely  under 
thirty-six  hours  from  the  farm.  The  difficulty  even  then  of 
furnishing  enough  leads  again  to  the  dilution  by  water,  either 
indirectly  through  the  breed  and  feed  of  the  cow  or  by  direct 
addition.  Again,  the  extensive  demand  for  cream  tends  to 
encourage  the  topping  of  the  milk. 

With  this  increase  in  quantity  and  in  time  of  keeping 
fresh  food  comes  also  the  danger  of  transmission  of  disease, 
which  constitutes  one  of  the  worst  dangers  in  food.  It  hap- 
pens with  considerable  frequency  that  thirty  or  forty  cases  of 
scarlet-fever  are  traced  to  a  single  farm;  that  typhoid-fever 
also  is  disseminated  in  the  milk.  Cream  and  butter  arc  also 
subject  to  suspicion.     During  the  years  1890  to  1899  nine 


142  AIR,    WATER,    AND    FOOD. 

experts  reported  on  339  samples  of  butter  and  found  tubercle 
bacilli  in  21  per  cent,  of  them. 

The  dangers  in  butter  are  largely  increased  by  the  prac- 
tice of  "  doubling  "  the  yield  by  a  treatment  of  milk  with 
rennet  and  salt,  "  black  pepsin,"  or  other  nostrums,  which 
works  a  large  proportion  of  curd  into  the  butter,  but  also 
renders  the  mass  much  more  liable  to  decomposition.  Since 
the  food  value  of  curd  is  only  half  that  of  fat,  and  since 
it  also  carries  more  water,  the  fraud  is  serious  on  both  sides. 

In  many  ways  the  bread-supply  of  a  city  needs  looking 
after  from  a  sanitary  and  economical  point  cf  view  quite  as 
much  as  the  milk-supply.  It  is  not  at  all  improbable  that, 
first  and  last,  as  much  disease  is  caused  l)y  bread  from  un- 
sanitary bakeries,  by  badly  baked  bread,  and  by  unduly  light 
bread  which  has  not  sufificient  food  value,  as  by  any  other 
cause. 

Summary. — The  chief  dangers  in  food  are  from  wrong 
proportions  of  proteid,  fat,  and  carbohydrates,  from  ferment- 
able and  irritating  decompositions,  from  bad  methods  of 
cooking  and  unsuitable  combinations,  from  transmission  of 
micro-organisms  either  by  exposure  to  dust  or  by  contact 
with  filthy  hands  or  vessels,  to  a  favorable  medium  for  the 
growth  of  pathogenic  germs. 

From  this  hasty  survey  it  will  be  seen  how  little  danger 
to  health  is  incurred  if  only  reasonable  care  is  taken  and  if 
the  always  doubtful  articles  are  avoided. 

Take,  for  instance,  that  most  commonly  adulterated  class, 
spices.  Who  will  say  that  it  may  not  be  better  to  eat  corn 
and  buckwheat  and  ground  peas  than  pure  pepper?  Rice 
is  certainly  a  more  wholesome  food  than  ginger,  and  starch 
than  soda.  Glucose  is  even  more  easily  absorbed  than  cane- 
sugar.  These  are  cases  of  frauds  on  the  pockets,  but  possible 
blessings   in   disguise   for  the    stomachs.     When   any   com- 


THE    PROBLEM    OF    SAFE   FOOD.  HS 

mtinity  is  so  ignorant  as  to  permit  of  such  gross,  out-of-date 
adulterations  as  alum  in  baking-powder,  and  gypsum  in 
cream  of  tartar,  they  deserve  to  suffer.  It  is  knowledge  on 
the  part  of  each  intelligent  citizen  which  will  mend  matters, 
even  if  it  is  only  that  kind  of  empirical  knowledge  that  one  is 
forced  to  learn  in  relation  to  electricity  and  steam  in  order  to 
live  in  a  modern  house. 

The  natural  food-materials  are  so  complex  in  composi- 
tion that  one  may  well  be  led  astray  by  outward  appearances, 
and  substances  of  the  same  proximate  composition  present 
themselves  under  so  many  guises  that  when  the  markets  of 
our  cities  ofifer  the  food  of  all  the  nations  of  the  earth,  how 
shall  the  buyer  know  what  he  is  getting?  To  outward  seem- 
ing, the  potato  and  the  banana  have  little  in  common,  but 
their  food  value  is  almost  identical,  with  the  advantage  on 
the  side  of  the  banana. 

The  general  public  is  alarmed  over  newspaper  reports 
not  wholly  disinterested,  or  is  "  instructed  "  by  paid  agents. 
People  become  accustomed  to  certain  terms  which  are  held 
up  as  scarecrows,  and  learn  to  look  to  the  daily  press  rather 
than  to  the  agricultural  college  for  knowledge  as  to  new 
or  dangerous  foods. 

The  remedy  lies  in  their  own  hands.  Every  high-school 
laboratory  should  contain  a  case  of  samples  and  charts 
of  values,  and  it  should  be  considered  just  as  impor- 
tant for  good  citizenship  that  the  child  should  have  the  tools 
of  health  put  in  his  hands  as  that  he  should  learn  about  bank- 
ing and  interest.  His  bank  account  is  his  health.  His  in- 
terest is  his  daily  efficiency. 

So  rapidly  do  new  substances  come  upon  the  market  that 
it  is  of  little  use  to  put  into  a  general  text-book  definite 
statements  of  the  quality  of  many  foods.  A  baking-powder 
or  a  spice  which  is  honestly  made  to-day  may  next  week  pass 


144  AIR,    WATER,    AND    FOOD. 

into  the  hands  of  unscriipiilous  dealers  who  please  the  public 
and  thereby  salve  their  consciences. 

To  furnish  what  the  people  think  they  want  has  been  the 
rule  from  the  days  of  an  earlier  generation  of  grocers,  who 
divided  a  barrel  of  cooking-soda  in  halves  and  set  one-half 
on  one  side  of  the  store  for  "  saleratus  "  and  the  other  on  the 
opposite  side  for  soda,  so  that  there  should  be  no  suspicion 
in  the  mind  of  the  customer  that  the  packages  came  from  the 
same  barrel,  and  yet  each  might  satisfy  his  individual  prefer- 
ence. 

We  wnsh  to  dwell  more  strongly  on  the  ethical  and  hy- 
gienic side  of  the  question  than  on  the  financial.  Evil-doers 
thrive  only  when  reputable  people  countenance  them. 
Adulterated  food  will  be  offered  only  so  long  as  buyers 
eagerly  take  it.  "  Those  that  hide  can  find."  If  science  is 
called  upon  to  sophisticate  food,  science  can  find  out  how  it 
is  done.  The  chemist  should  be  so  grounded  in  morals  as 
to  refuse  to  sell  his  knowledge  for  a  manufacture  which  is 
dangerous  to  health.  We  have  tried  to  show  that  it  is  not 
very  frequently  the  case  that  the  manufactured  article  is  of 
itself  directly  injurious,  only  in  its  misuse. 

It  may  be  a  question  which  is  the  cheaper,  to  build  a  sub- 
way or  to  kill  a  few  persons  now  and  then  by  the  surface 
cars.  So  in  food,  it  is  necessary  either  to  put  an  elaborate 
machinery  of  inspectors  and  chemists  and  courts  in  motion. 
at  great  expense,  or  to  educate  the  people  at  large  so  that 
each  will  be  his  own  inspector.  The  latter  is  more  in  har- 
mony with  American  practice,  but  the  economic  conditions  in 
other  directions  are  pressing  the  food-supply  into  the  same 
channels  as  clothing,  furniture,  and  transportation;  that  is, 
away  from  individual  control  as  to  manufaclurc.  This  neces- 
sitates individual  knowledge  in  purchasing  if  satisfactory  re- 
sults are  to  follow. 


THE    PROBLEM    OF   SAFE    FOOD.  145 

This  knowledge  is  now  easily  obtained  through  the  city, 
State  and  government  laboratories,  and  their  publications 
are  accessible  to  all  who  can  read  and  write.  There  is,  there- 
fore, no  excuse  for  general  ignorance  and  credulity  as  to 
trade  preparations  of  foods,  any  more  than  for  the  degrading 
habit  of  purchasing  patent  medicines  to  remedy  the  ills 
caused  by  the  misuse  of  food.  Both  together  form  the  sad- 
dest commentary  on  human  weakness  and  lack  of  rational 
thought 


CHAPTER    X. 


ANALYTICAL    METHODS. 


In  the  discussion  of  the  methods  employed  for  the  ex- 
amination of  food-materials,  only  a  few  typical  substances 
have  been  considered,  and  the  processes  given  are  such  as  to 
bring  into  prominence  the  scientific  aspect  rather  than  the 
technical  detail  of  the  subject;  at  the  same  time  it  is  hoped 
that  a  suf^cient  variety  of  methods  is  given  to  enable 
the  student  to  gain  considerable  experience  in  the  necessarily 
short  time  which  can  be  allotted  to  the  subject. 

Both  on  account  of  its  importance  as  a  food-material  and 
on  account  of  its  availability  for  the  various  tests,  milk  has 
been  chosen  as  a  type  of  animal  food;  moreover,  it  may  be 
made  to  serve  as  an  excellent  example  of  the  changes  to 
which  food-materials  are  liable  through  the  growth  of  the 
micro-organisms.  The  analysis  of  milk  includes  determina- 
tions of  specific  gravity,  water,  or  total  solids,  ash,  fat,  nitro- 
gen, and  sugar,  together  with  the  separation  of  casein  and 
albumin,  the  determination  of  the  products  of  putrefaction 
and  fermentation,  namely,  ammonia  and  acidity,  also  the  de- 
tection of  preservatives  and  coloring  matters. 

Wheat  is  taken  as  a  type  of  vegetable  foods.  The  ex- 
amination which  may  be  made  of  this  class  includes  the  de- 
termination of  moisture,  ash,  fat,  nitrogen  and  proteids, 
starch,    cellulose,   and   the   products   of   peptonization   and 

saccharification. 

146 


food:  analytical  methods:  milk.  147 

The  nature  and  composition  of  the  various  fats  and  oils 
is  briefly  illustrated  by  the  examination  of  butter  and  the  de- 
termination of  the  principal  constants  of  the  butter-fat. 

The  results  of  fermentation  are  illustrated  by  the  deter- 
mination of  alcohol  in  beer,  wine,  meat  extracts,  patent  medi- 
cines and  "  temperance  drinks,"  flavoring  essences  and  the 
like.  The  determination  of  the  acidity,  of  the  "  extract,"  and 
of  nitrogen  is  also  sometimes  desirable. 

Condiments,  spices,  tea,  and  coffee  are  generally  exam- 
ined by  means  of  microscopic  tests,  but  adulterations  of 
these,  as  of  most  common  groceries,  affect  the  health  less 
than  the  pocket.  Text-books  on  food  adulteration  furnish 
sufficient  information  on  these  points.  (See  Bibliography, 
P-  213.) 


MILK. 

General  Statements. — Milk  is  an  emulsion  of  fat-globules 
with  casein  and  other  nitrogenous  bodies,  mineral  salts 
(probably  in  combination),  sugar  and  water.  The  average 
percentage  composition  of  the  more  important  varieties  of 
milk,  as  found  by  recent  observers,  is  summarized  in  the  fol- 
lowing table: 

Water.  Sugar.  Proteids.  Fat.  Ash. 

Cow 86.90  4.80  3.60  4.00  0.70 

Human 88.75  6.00  1.50  3.45  0.30 

Goat 85.70  4.45  4-30  4-75  0.80 

Ass 8g.50  6.25  2.00  1.75  0.50 

Mare 90.75  5-7o  2.00  1.20  0.35 

Sheep 80.80  4.90  6.55  6.85  0.90 

In  connection  with  this  table  should  be  noticed  the  high 
proportion  of  sugar  and  low  proportion  of  casein  and  ash  in 
human  milk  as  compared  with  cow's  milk.  The  former  is  not 
readily  curdled,  the  casein  never  separating  in  a  compact  clot 


148  AIR,    WATER,    AND    FOOD. 

which  settles  to  the  bottom,  a  difference  which  is  attributed 
to  the  lower  proportion  of  fat  to  casein.* 

The  average  composition  of  120,540  samples  of  cow's 
milk,  extending  over  a  period  of  eleven  years,  and  the  aver- 
age composition  of  14,135  samples  of  cow's  milk  for  the 
year  1898,  analyzed  directly  on  arrival  of  the  milk  from  the 
farm,  is  given  by  \'ieth  and  Richmond  f  as  follows: 

Average,  1898.  Average  of  eleven  years. 

Specific  gravity 1.0320 

Total  solids 12.73  12.90 

Solids  not  fat 8.90  8.80 

Fat 3.83  4.10 

An  examination  of  milk  as  regards  its  healthf illness  usually 
consists  in  determining  what  changes,  if  any,  have  taken  place 
in  its  constituents  due  to  the  growth  of  micro-organisms. 
Milk  is  a  natural  culture  medium  for  the  growth  of  micro- 
organisms and  they  increase  in  it  with  almost  incredible 
rapidity.  These  changes  which  take  place  are  called  "  fer- 
mentations." The  two  most  common  are  the  acid  and  the 
alkaline. 

Acid  Fermentation. — ]\Iilk-sugar  is  converted  wholly  or  in 
part  into  lactic  acid  under  the  influence  of  a  class  of  organisms 
of  which  bacillus  acidi  lactici  is  the  best  known  and  is  generally 
regarded  as  predominating.  The  extent  to  which  this  change 
has  taken  place  is  shown  by  the  test  for  acidity. 

Alkaline  Fermentation. — In  the  alkaline  fermentation  the 
albumin  and  casein  are  decomposed  with  the  formation  of 
ammonia  and  other  intermediate  nitrogenous  products,  some 
of  them  of  a  poisonous  character,  as  is  shown  by  the  preval- 
ence of  cholera  infantum  when  such  decomposed  milk  is  used, 

*  Lehmann  and  Hempel:  Arch.  Physiol.,  56  (/Sg4),  558. 
f  Analyst,  17  {i8g2),  84;  24  {i8gg),  197. 


food:     analytical    METHODS:     MILK.  I49 

and  by  cases  of  poisoning  by  ice-cream,  etc.  This  fermenta- 
tion generally  occurs  simultaneously  with  the  acid  fermen- 
tation, but  at  first  is  much  less  active;  at  a  subsequent  stage, 
however,  the  alkaline  fermentation  becomes  more  pro- 
nounced, and  in  certain  cases  may  completely  dominate  the 
other  fermentations. 

Other  Fermentations. — Butyric  acid  fermentation  may  be 
a  result  of  the  action  of  one  or  several  groups  of  bacteria  upon 
the  glyceride  of  butyric  acid.  This  action  sets  free  the  butyric 
acid  in  part  and  the  fat  becomes  in  time  '*  rancid,"  but  this 
change  takes  place,  as  a  rule,  more  slowly  and  is  not  so  com- 
mon as  the  others. 

The  production  of  koumiss  is  an  instance  of  an  artificially 
incited  change.  Various  other  fermentations  occasionally 
occur  which  cause  a  slimy  appearance  or  a  bitter  taste. 
Various  colors  may  be  imparted  to  the  milk  by  the  presence 
of  cJiromogenic  or  color-producing  micro-organisms.  The 
student  is  referred  to  the  various  journals  and  to  text-books 
on  dairy  bacteriology  for  accounts  of  these  less  important 
changes. 

Sampling. — In  all  manipulations  with  milk  the  importance 
of  thorough  and  frequent  mixing,  not  shaking,  cannot  be  too 
strongly  emphasized;  this  is  best  accomplished  by  pouring  it 
from  one  vessel  to  another.  This  will  be  found  necessary 
even  when  the  milk  has  been  standing  for  only  a  few  minutes, 
on  account  of  the  rapid  rise  of  the  cream.  The  apparatus 
used  to  contain  or  to  measure  milk  should  be  thoroughly 
washed  out  as  soon  as  possible. 

PHYSICAL    TESTS. 

Specific  Gravity. — Take  the  specific  gravity  in  the  usual 
manner  by  means  of  a  hydrometer  or  by  the  Westphal  bal- 
ance, at  15°  C.     If  the  temperature  of  the  milk  varies  from 


1.50  AIR,    WATER,    AND    FOOD. 

15°,  the  reading  may  be  corrected  by  means  of  Table  IX,  Ap- 
pendix A.  Take  a  reading  of  the  lactometer  at  the  same  time. 
In  this  instrument  the  minimimi  density  for  whole  milk  is 
fixed  at  100,  corresponding  to  a  specific  gravity  of  1.029. 

JSlotes. — The  specific  gravity  of  milk  is,  in  the  main,  a  func- 
tion of  two  factors,  namely,  the  percentage  of  solids  not  fat 
and  of  the  fat.  The  former  raises  it;  the  latter  lowers  it.  The 
determination  of  the  specific  gravity  alone  is  not  to  be  relied 
upon  as  an  absolute  index  of  the  purity  of  the  milk.  The 
specific  gravity  varies  in  general  from  1.029  to  1.034,  and  in 
most  cases  of  normal  and  well-mixed  milk  from  several  cows 
the  specific  gravity  will  lie  between  1.030  and  1.032. 

Opacity.  —  The  white  color  and  opacity  of  milk  are 
largely  due  to  the  presence  of  the  suspended  fat-globules  and 
of  the  casein  in  colloidal  form.  The  influence  of  the  latter  is 
shown  by  the  fact  that  the  color  of  milk  is  not  greatly 
changed  after  it  has  passed  through  a  centrifugal  separator 
which  removes  practically  all  of  the  fat.  The  degree  of 
opacity  and  the  percentage  of  fat  may  be  determined  by 
means  of  Feser's  lactoscope,  the  modus  operandi  of  which  is 
given  with  that  instrument.  Another  instrument  of  like  prin- 
ciple is  Heeren's  pioscope,*  which  consists  of  an  ebonite  disk 
with  a  raised  rim;  a  drop  or  two  of  milk  is  placed  upon  it,  the 
painted  glass  cover  placed  over  it,  and  the  color  of  the  milk 
matched  with  one  of  those  on  the  cover. 

Cream. — Fill  the  creamometer,  an  elongated  test-tube 
Avith  graduations  near  the  top,  to  the  zero  mark  with  the 
milk,  add  three  drops  of  a  solution  of  methyl  violet,  mix  and 
put  away  in  a  cold  place.  After  twenty-four  hours  read  off 
the  percentage  of  cream. 

]\Totcs. — The  rapidity  with  which  the  cream  rises  indicates 


*  Eepit.  f.  Anal.  Chent.,  l88i,  247. 


food:     analytical    METHODS:     MILK.  151 

whether  sodium  carbonate  has  been  added,  its  action  being 
to  retard  the  rise  of  cream  so  that  the  milk  is  never  blue. 
Should  the  cream  separate  very  quickly  and  the  milk  be  blue, 
the  indication  is  that  water  has  been  added  or  that  the  milk 
is  of  poor  quality.  The  method  is  only  approximate  and  does 
not  give  the  amount  of  fat.  The  methyl  violet  is  added  to 
render  the  reading  sharper,  as  it  does  not  dissolve  appreciably 
in  the  cream.  Cream  contains  most  of  the  fat  of  milk  with  a 
small  proportion  of  the  other  constituents.  loio  samples  of 
cream  gave  an  average  of  48.3  per  cent.  fat. 

*  CHEMICAL  TESTS. 

Reaction. —  Normal  milk  gives  the  amphoteric  reaction, 
that  is,  it  turns  delicate  litmus  both  red  and  blue.  This  is  due 
to  the  presence  of  neutral  and  acid  phosphates  of  the  alkalies. 
The  reaction  of  the  milk  soon  becomes  acid,  however. 

Acidity.  —  Measure  5  c.c.  of  milk  into  a  small  beaker, 

N 
dilute  with   so  c.c.  of  water,  and  titrate  the  acid  with  — 

10 

sodium  hydroxide,  using  phenolphthalein  as  an  indicator. 
Express  the  acidity  in  degrees,  considering  each  tenth  of  a 
cubic  centimeter  of  sodium  hydroxide  one  degree. 

Notes. — The  acidity  of  milk  is  due  to  the  fermentation  of 
milk-sugar  and  the  production  of  lactic  acid.  Under  favor- 
able circumstances  this  change  may  take  place  with  consid- 
erable rapidity.  For  example,  six  hours  after  milking  the 
acidity  may  be  fourteen  to  twenty-five  degrees;  forty-eight 
hours  after  milking  it  may  reach  one  hundred  degrees.  When 
the  acidity  reaches  twenty-three  degrees  milk  coagulates  on 
boiling.*  An  example  of  the  rate  of  change  is  given  in  the 
following  table:  f 

*  Thorner:  Analyst,  l6  {i8gi),  200. 

t  ••  Thesis,"  Elhel  B.  Blackwell,  M.I.T.,  1891. 


152  AIR,    WATER,    AND    FOOD. 

_,  Acidity,  Sugar, 

L>^7-  c.c.  Degrees  of  Rotation. 

1 2.2  25.2 

2 5-5  23.1 

3 II. o  21.6 

6 13-2  14-2 

7 150  9-4 

8 16.3  7-8 

9 17-2  1.2 

Alkalinity. —  Directions. — Measure  into  a  750-c.c.  round- 
bottomed  flask  25  c.c.  of  the  milk.  Add  350  c.c.  of  ammonia- 
free  water  and  0.5  gram  of  sodium  carbonate  and  distil  over 
about  200  c.c.  into  a  flask  containing  about  20  c.c.  of  dilute 
sulphuric  acid  (1:40).  Neutralize  the  distillate  with  sodium 
carbonate  and  redistil  it,  receiving  the  distillate  into  15  c.c. 

N 
Cmeasured)  of  —  hvdrochloric  acid.     Titrate  the  excess  of 
^  "^        10     ' 

N 
acid   with   —  sodium   hvdroxide,   using  methyl   orange   or 
10 

cochineal  as  an  indicator. 

Notes. — In  the  alkaline  fermentation  the  proteids  of  milk 
are  decomposed  through  the  growth  of  micro-organisms. 
Ammonia,  or  some  substance  which  yields  ammonia  on  dis- 
tillation, is  formed  and  tends  to  neutralize  the  lactic  acid. 
On  the  other  hand,  alnmdant  acid  tends  to  check  the  growth 
of  the  alkaline  ferments.  It  depends  upon  certain  conditions 
of  seeding  and  of  temperature  as  to  which  gets  the  best  start 
in  the  race.  It  is  to  the  alkaline  fermentation  that  most  of 
the  danger  in  using  unsterilized  milk  is  due. 

The  second  distillation  which  is  made  is  for  the  purpose 
of  converting  into  ammonia  any  amines  which  may  have  been 
formed  during  the  first  distillation. 

Total  Solids. — The  determination  of  total  solids  is  best 
carried  out  in  a  platinum  dish  having  a  flat  bottom  about  2^ 
inches  in  diameter.  Small  dishes  of  aluminum  or  blacking- 
box  covers  answer  very  well,  but  of  course  cannot  be  ignited 
to  obtain  the  ash. 

Directions. — Weigh  the  platinum  dish  and  add  about  5.1 


food:   analytical  methods:   milk.  153 

grams  to  the  weights  on  the  balance-pan.  With  the  burette 
pipette  deHver  5  c.c.  of  the  well-mixed  milk  into  the  dish  and 
weigh  the  whol'e  as  rapidly  as  possible  to  the  nearest  milli- 
gram. Evaporate  the  milk  to  dryness  on  the  water-bath  and 
then  dry  it  in  the  oven  at  100°  to  a  constant  weight.  Some 
analysts  recommend  drying  at  105°  for  three  hours  instead  of 
to  constant  weight. 

^^otcs. — It  is  important  that  the  milk  should  be  in  the  form 
oi  a  thin  layer,  so  that  the  evaporation  of  the  water  shall  take 
place  as  quickly  as  possible.  Under  these  conditions  the  resi- 
due obtained  is  nearly  white;  but  if  the  process  be  prolonged, 
it  may  have  a  brownish  color  from  the  caramelization  of  the 
sugar. 

Various  analysts  have  proposed  modifications  of  the  pro- 
cedure as  described  above,  such  as  drying  on  sand  or  asbes- 
tos, coagulation  of  the  milk  by  absolute  alcohol  before  evapo- 
ration, and  so  forth,  but  simple  evaporation  in  an  open  dish 
is  generally  regarded  as  the  most  advantageous. 

Ash. —  Directions. — Ignite  the  platinum  dish  containing 
the  residue  from  the  preceding  determination  at  a  low  red 
heat  until  the  ash  is  white  or  nearly  so.  In  order  to  avoid 
too  great  a  heat  it  is  best  to  finish  the  ignition  in  a  "  radia- 
tor," as  in  the  determination  of  the  fixed  residue  in  water- 
analysis.  After  weighing  the  ash,  test  it  for  carbonates  by 
adding  two  drops  of  dilute  hydrochloric  acid.  Effervescence 
in  the  ash  is  quite  perceptible  when  carbonates  are  present  in 
as  small  amount  as  0.05  per  cent.  If  desired,  the  hydrochloric 
acid  solution  of  the  ash  can  be  used  to  test  for  boric  acid  as 
described  on  page  168. 

Notes. — If  the  temperature  is  raised  too  much  during 
ignition,  the  results  will  be  low  on  account  of  the  partial  vola- 
tilization of  the  chlorides  of  the  milk;  hence  the  process 
should  be  carried  out  at  as  low  a  temperature  as  will  admit  of 
the  oxidation  of  the  carbonaceous  matter. 


154  AIR,    WATER,    AND    FOOD. 

The  percentage  composition  of  the  ash  of  milk  is  given 
by  Fleischmann  and  Schrodt  *  as  follows: 

Per  cent. 

Potassium  oxide,  KjO 25.42 

Sodium            "        Na,0 10.94 

Calcium          "       CaO 21.45 

Magnesium    "       MgO 2.54 

Ferric              "       FeaOs o.ii 

Sulphuric  acid,      SO3 4-ii 

Phosphoric  "         PaOs 24.11 

Chlorine,                CI i4-6o 

103.23 
Less  oxygen  corresponding  to  chlorine}      3-28 

100.00 

The  aoh  of  genuine  cow's  milk  is  free  from  carbonates  and 
borates,  and  the  ash  soluble  in  water  is  about  30  per  cent,  of 
the  total. 

Fat.  —  Since  the  fat  is  so  important  a  constituent  of  milk, 
an  endless  variety  of  methods  and  modifications  for  its  deter- 
mination have  been  devised.  The  processes  which  are  in 
most  general  use  may  be  divided  into  three  classes: 

1.  Estimation  of  the  fat  by  simple  extraction  of  the  milk, 
best  dried  on  some  absorbent  material. 

2.  Volumetric  estimation  of  the  fat  liberated  by  chemical 
treatment  from  the  milk  and  collected  by  centrifugal  force. 

3.  Estimation  of  the  fat  by  extraction  from  the  milk  itself 
■after  solution  of  the  casein  by  acid. 

A  typical  method  from  each  class  will  be  described  in  de- 
tail. 

(i)  Adams'  Method.  —  Directions. — Roll  a  strip  of  fat- 
free  blotting-paper,  22  inches  long  and  2|  inches  wide,  into 

*Baumeister:  "Milch  und  Molkerei-Producte,"  S.  i6. 

+  This  correction  is  necessary  because  the  metals  are  all  calculated  as 
oxides,  when,  as  a  matter  of  fact,  a  certain  proportion  are  present  as 
chlorides. 


food:     analytical    METHODS:     MILK.  155 

a  rather  loose  coil  and  fasten  it  by  a  bit  of  copper  wire.  Hold 
the  coil  in  one  hand  and  carefully  run  on  to  the  upper  end  of 
it  5  c.c.  of  milk  from  a  burette  pipette.  Place  the  coil,  dry 
end  downward,  in  the  water-oven  and  dry  it  for  an  hour. 
When  dry  remove  the  wire  and  place  the  coil  in  the  Soxhlet 
extractor.  If  preferred,  the  strip  of  paper  may  be  held  hori- 
zontally in  a  frame  and  the  milk  run  on  to  it.  When  dry  the 
paper  is  rolled  into  a  coil  and  extracted.  Weigh  the  extrac- 
tion-flask, place  in  it  75  to  100  c.c.  of  86°  gasolene  (petroleum 
ether)  and  connect  the  extractor  with  the  condenser.  After 
the  coil  has  been  extracted  for  about  two  hours  remove  the 
extractor,  connect  the  flask  with  the  suction  if  it  is  at  hand, 
and  distil  off  the  gasolene  under  reduced  pressure.  The  in- 
crease in  weight  of  the  flask  gives  the  fat.  Oxidation  of  the 
fat  by  too  long  heating  should  be  avoided. 

Notes. — Absorbent  paper  exercises  a  selective  action  on 
the  constituents  of  milk  so  that  the  fat  is  left  on  the  surface 
of  the  paper,  mixed  with  only  about  one-third  of  the  non-fatty 
solids,  and  hence  it  is  more  easily  extracted;  further,  owing 
to  the  greatly  increased  surface  exposed,  the  extraction  of  the 
fat  is  practically  complete. 

Ether  may  be  used  instead  of  gasolene,  but  care  should 
be  taken  that  the  ether  is  perfectly  dry,  otherwise  other  sub- 
stances than  fat,  principally  milk-sugar,  will  be  extracted.  On 
the  other  hand,  substituted  glycerides  may  not  be  dissolved 
out  by  ether.  For  these  reasons  the  gasolene  is  to  be  pre- 
ferred as  a  solvent,  although  its  action  is  considerably  slower 
than  that  of  the  ether. 

Owing  to  the  inflammable  nature  of  the  solvents  em- 
ployed, it  is  best  not  to  use  a  flame  as  the  source  of  heat,  but 
to  heat  the  flask  by  means  of  a  steam-  or  water-bath.  In  this 
laboratory  small  electric  heaters  about  4  inches  in  diameter 
are  used  and  have  been  found  safe  and  convenient.  The  com- 
plete apparatus  is  shown  in  Fig.  7. 


156 


AIR,    WATER,    AND    FOOD. 


Another  form  of  apparatus,  devised  by  \V.  R.  Whitney, 
which  has  been  used   with  satisfactory  results  is  shown  in 


WATER 


Fig.   7. — Apparatus  for  Fat  Extraction. 

Fig-.  8.  It  consists  of  an  ordinary 
test  tube,  the  lower  part  of  which 
is  heated  by  a  steam  coil.  A  coil  of 
small  brass  tubing-,  carrying  a  stream 
of  cold  water,  hangs  in  the  mouth  of 
the  test  tube  and  serves  as  a  conden- 
ser. The  paper  coil  hanging  from  the 
condenser  is  extracted  by  the  use  of 
about  10  c.c.  of  gasolene  or  ether. 

(2)  Babcock  Method. — Directions. 
— Measure  17.6  c.c.  of  the  milk  from  a 
o -STEAM COIL-  pipette  into  the  long-necked,  gradu- 
ated whirling-bottle.  Measure  out 
17.5  c.c.  of  sulphuric  acid  (sp.  gr. 
1.83),    and    add    it    gradually    to    the 

milk,    mixing    the    two    thoroughly    after    each    addition. 

Take    care   that    none   of   the   liquid    spurts   into    the   neck 


GASOLENE 


food:     analytical    METHODS:     MILK.  1 5/ 

of  the  bottle.  After  mixing  the  milk  and  acid,  and 
while  the  bottles  are  still  hot,  place  them  in  opposite 
pockets  in  the  centrifugal  machine,  in  even  numbers, 
and  whirl  them  for  six  minutes,  the  large  wheel  making 
eighty  to  ninety  revolutions  per  minute.  Then  remove  the 
bottles  and  add  hot  water  until  the  fat  rises  to  the  8  mark  on 
the  stem.  Again  place  the  bottles  in  the  machine  and  whirl 
them  at  the  same  rate  as  before  for  one  minute.  Then 
measure  the  length  of  the  column  of  fat  by  a  pair  of  dividers, 
the  points  being  placed  at  the  extreme  limits  of  the  column, 
the  fat  being  kept  warm,  if  necessary,  by  standing  the  bottle 
in  hot  water.  If  now  one  point  of  the  dividers  is  placed  at 
the  zero  mark  of  the  scale  on  the  bottle  used,  the  other  will 
indicate  the  per  cent,  of  fat  in  the  milk. 

Notes. — \\'hen  the  acid  and  milk  are  mixed  the  mixture 
becomes  hot  from  the  action  of  the  acid  on  the  water  in  the 
milk  and  turns  dark-colored  on  account  of  the  charring  of 
the  milk-sugar.  The  casein  is  first  precipitated  and  then 
dissolved.  The  fat  is  thus  separated  in  a  pure  state  from 
the  other  constituents  of  the  milk. 

The  fat  obtained  should  be  of  a  clear,  golden-yellow  color, 
and  distinctly  separated  from  the  acid  solution  beneath  it. 
If  the  fat  is  light-colored  or  whitish,  it  generally  indicates 
that  the  acid  is  too  weak,  and  a  dark-colored  fat  with  a 
stratum  of  black  particles  below  it  indicates  that  the  acid  is 
too  strong.  The  best  results  will  be  obtained  by  the  use  of 
acid  of  the  strength  noted  above. 

A  violet  color  is  sometimes  produced  when  the  first  por- 
tions of  the  acid  and  milk  are  mixed.  This  frequently  indi- 
cates the  presence  of  formaldehyde.  (See  p.  i68.) 
•  (3)  Werner-Schmid  Method. — Directions. — Measure  lo 
c.c.  of  milk  into  a  long  test-tube  of  50  c.c.  to  60  c.c.  capacity 
and  add   10  c.c.  of  hydrochloric  acid  (sp.  gr.   1.20).     Place 


158 


MR,    WATKR.    AND    FOOD. 


the  tube  in  l)oiling-  water  and  Iieat,  with  frequent  shakings 
until  the  liquid  turns  dark  brown,  which  generally  requires 
about  ten  minutes.  Do  not  heat  it  so  long  that  the  liquid 
turns  black.  Cool  the  tube  thoroughly  under  the  tap,  add 
30  c.c.  of  washed  ether  or  of  a  mixture  of  equal  parts  ether 
and  petroleum  ether,  cork  tightly  and  mix  we'd  by  inverting 
the  tube.  Allow  the  tube  to  stand  for  a  few  minutes  for  ihe 
complete  separation  of  the  ethereal  layer,  then  remove  the 
cork  and  transfer  the  ether  to  a  tared  llask  by  means  of  the 
apparatus  shown  in  Fig.  9.  This  consists  of  a  cork  carrying 
an  ordinary  glass  T  tube.  Through  the 
straight  limb  of  the  T  tube  slides  a  bent 
glass  tube,  which  is  turned  up  at  the  lower 
end.  The  tube  is  adjusted  by  sliding  it 
through  the  rubber  collar  (C)  so  that  the 
lower  end  rests  just  above  the  junction  of 
the  two  layers.  On  then  blowing  gently 
in  the  side  arm  (S),  the  upper  layer  is 
forced  ou."  into  the  flask.  Repeat  the  ex- 
traction three  times  after  the  first,  using 
10  c.c.  of  ether  each  time  and  blowing  it 
ofif  into  the  flask.  Distil  ofif  the  ether,  dry 
the  residual  fat  and  weigh. 

Notes. — It  is  almost  useless  to  try  to  ex- 
tract the  fat  from  milk  by  shaking  it  directly  with  a  solvent. 
An  emulsion  is  formed  with  the  other  constituents  of  the 
milk,  and  it  is  impossible  to  get  a  good  separation  of  the 
solvent  even  with  the  centrifugal  machine.  This  is  probably 
due  to  the  action  of  the  colloidal  casein,  because  it  is  found 
that  w^hen  a  complete  or  partial  solution  of  the  casein  is 
effected  it  is  comparatively  easy  to  extract  and  separate  the 
fat  by  a  solvent  immiscible  with  water. 

The  ether  which  is  employed  should  be  well  washed  to 


food:   analytical  methods:   milk.  159 

remove  alcohol,  and  the  heating  with  hydrochloric  acid 
should  not  be  continued  too  long  on  account  of  the  liability 
of  forming  caramel  products  which  dissolve  in  the  ether. 
For  that  reason  the  process  is  not  so  well  suited  for  use  with 
condensed  or  highly  sugared  milks.  Since  lactic  acid  is 
slightly  soluble  in  ether,  it  is  better  when  working  with  sour 
milk  to  make  the  extraction  with  petroleum  ether  or  a  mix- 
ture of  petroleum  ether  and  ordinary  ether. 

Relation  between  Specific  Gravity,  Fat,  and  Solids 
in  Milk. — As  has  been  stated  already,  the  specific  gravity 
of  milk  is,  in  the  main,  a  function  of  two  factors,  namely, 
the  percentage  of  solids  not  fat  and  that  of  the  fat.  The  former 
raises  it,  the  latter  lowers  it.  Taken  by  itself  it  affords  very 
little  indication  of  the  composition,  but  if  any  other  item  be 
known,  it  should  be  possible  to  find,  by  calculation,  the  other 
quantities,  provided  the  assumption  is  true.  The  solids  not 
fat  are  made  up  of  several  fluctuating  constituents,  but  "  nor- 
mal milk  "  seems  to  contain  them  in  such  a  constant  ratio 
that  a  calculation  serves  at  least  to  detect  an  abnormal  sam- 
ple. For  example,  given  the  specific  gravity  and  solids  to 
calculate  the  fat: 

Specific  gravity  =  Gr.  The  amount  which  each  per  cent, 
of  solids  not  fat  raises  the  specific  gravity  =  s.  The  amount 
which  each  per  cent,  of  fat  lowers  the  specific  gravity  =  f. 
Total  solids  =  T.  Solids  not  fat  =  S.  Fat  =  F.  Gr  =  Ss 
—  Ff;  or,  substituting  for  S  its  value  T  —  F;  Gr  =  (T  —  F) 
.y  —  Ff.  The  uncertainty  of  the  calculation  lies  in  the  val- 
ues of  s  and  f,  which  have  not  been  quite  satisfactorily  deter- 
mined. 

At  different  times  various  formuk-e  have  been  proposed 
for  this  calculation,  varying,  as  a  matter  of  course,  with  the 
method  of  fat  extraction  employed.     The  one  most  extcn- 


I60  AIR,    WATER,    AND    FOOD. 

sively  used  is  that  of  Hehner  and  Richmond,*  which  is  based 
on  extensive  observation  and  perfected  processes  of  fat  ex- 
traction.   This  formula  is  generally  stated  as  follows: 

F  =  o.SsgT-  0.21S6G, 

where /^represents  the  fat,  T'the  total  solids,  and  G  looo  X 
(specific  gravity  —  i.ooo). 

The    simple    formula    -F  =   T  —   —  answers  within   the 
5  4 

limits  of  experimental  error  for  normal  milk,  but  not  for 
skimmed  or  watered  milk. 

£xam/>/i\ — Data  :  Gr  =  1.0323  ;  G  =  {Gr  —  i)  X  1000  = 
32.3;    r=  12.90. 

6  32.3 

-F  =  12.90  —  - — -.     F=4.02  calculated,     3.99  found. 

5  4 

A  similar  relation  has  been  worked  out  for  the  proteids 
and  sugar,  so  that  from  three  determinations  the  whole  com- 
position may  be  calculated.     Example  as  above: 

Ash     =  .70  =  A. 

Formula:   /^  =  2.8  r+ 2.5^  —  3.33/^— .68-^, 

Gr. 

or  /*=  36. 12  4-  1-75  —  13.32  —  21.28  =  3.27. 

Sugar  =:T—{A-{-  P-\-  F) 

=   12.90  -  (.70  +  3.27  +  4.02)  z=  4.91. 

Where  a  number  of  calculations  are  to  be  made,  Rich- 
mond's milk-scale  will  be  found  convenient.  This  is  an  in- 
strument based  on  the  principle  of  the  slide-rule,  havmg  three 
scales,  two  of  which,  for  the  fat  and  the  total  solids,  are 
marked  on  the  body  of  the  rule,  while  t-bat  for  the  specific 
gravity  is  marked  on  the  sliding  part.  Extended  tables  are 
also  used  for  the  same  purpose. 

*  Analyst,  13  {1888),  26;   17  {i8g2),  170. 


food:     analytical    METHODS:     MILK.  l6l 

Milk-sagar.  — The  methods  for  the  determination  of  the 
sugar  in  milk  may  be  divided  into  two  general  classes:  (i) 
those  depending  on  the  reducing  power  of  the  sugar  upon  an 
alkaline  copper  solution;  (2)  those  which  are  based  upon  ob- 
servations of  the  degree  of  rotation  of  the  plane  of  polarized 
light. 

(i)  Determination  by  F^hling's  Solution. 

(a)   Volumetrically. 

Directions. — The  milk  must  first  be  clarified  to  remove 
substances  other  than  sugar  which  would  exert  a  reducing 
action  on  the  Fehling's  solution.  To  do  this,  measure  25  c.c. 
of  milk  from  a  pipette  into  a  250-c.c.  bottle.  Add  0.5  c.c. 
(measured)  of  25  per  cent,  acetic  acid,  shake  vigorously,  and 
allow  it  to  stand  for  five  minutes.  Add  75  c.c.  boiling  dis- 
tilled water,  shake,  and  let  it  stand  two  or  three  minutes.  Add 
15  c.c.  of  milk  of  alumina  (see  determination  of  chlorine  in 
water),  shake,  and  allow  the  bottle  to  remain  on  its  side  for 
ten  minutes.  Decant  carefully  into  a  medium-sized  beaker, 
and  add  hot  water  again  to  the  residue  in  the  bottle.  Decant 
the  liquid  from  the  beaker  on  to  a  ribbed  Swedish  filter.  Wash 
thus  by  successive  decantations  from  the  bottle  to  the  beaker, 
and  thence  to  the  filter  several  times  before  bringing  the 
precipitate  on  the  filter.  Make  the  filtrate  up  to  500  c.c.  and 
mix  thoroughly.  The  solution  should  be  perfectly  clear  and 
almost  without  color. 

Titration. — Measure  5  c.c.  of  the  copper  solution  from  a 
burette  into  a  150-c.c.  Erlenmeyer  flask,  add  5  c.c.  of  the 
alkaline  tartrate  solution  and  40  c.c.  of  water.  Heat  to  boil- 
ing and  from  a  burette  run  in  the  sugar  solution,  as  prepared 
above,  as  long  as  a  blue  color  is  seen  in  the  liquid,  which 
must  be  kept  constantly  boiling.  When  the  end-point  is  ap- 
parently reached,  test  the  solution  for  copper  by  filtering  a 


l62  AIR,    WATER,    AND    FOOD. 

few  drops  through  a  very  small  filter  on  to  a  porcelain 
plate  containing  a  dilute  solution  of  potassium  ferrocyanide 
strongly  acidulated  with  acetic  acid,  when,  if  copper  be  pres- 
ent, the  characteristic  rose  coloration  will  appear.  This  will 
give  approximately  the  number  of  cubic  centimeters  required 
to  decolorize  the  copper  solution. 

To  find  the  exact  number,  add  the  quantity  of  sugar  solu- 
tion used  above  to  a  fresh  portion  of  5  c.c.  of  each  solution 
and  40  c.c.  of  water,  boil  exactly  two  minutes,  and  test  the 
solution  for  copper  as  before.  If  copper  be  still  present,  re- 
peat the  operation,  using  0.2  c.c,  more  or  less,  of  the  sugar 
solution  each  time  until  the  end-point  is  reached.  If  10  c.c. 
of  Fehling's  solution  of  the  strength  given  are  reduced  by 

^  f      -11  u  500  X  .067 

0.067  gram  of  milk-sugar,  then  t-—. u  =  grams 

'    °  ^  c.c.  solution  used 

of  milk-sugar  in  25  c.c.  of  the  milk.    The  results  are  reported 

in  per  cent.    From  27  to  34  c.c.  of  the  milk-sugar  solution  are 

usually  required  to  reduce  10  c.c.  of  Fehling's  solution. 

Notes. — The  general  principle  upon  which  all  these 
methods  depend  is  based  on  the  fact  that  certain  sugars, 
among  which  is  lactose,  have  the  power  of  reducing  an  alka- 
line solution  of  copper  to  a  lower  state  of  oxidation  in  which 
copper  is  separated  as  cuprous  oxide.  The  copper  salt  which 
is  found  to  give  the  most  delicate  and  reliable  reaction  is  the 
tartrate.  The  two  solutions  which  make  up  the  Fehling's 
solution  are  best  presented  separately,  and  mixed  only  when 
wanted  for  use,  as  otherwise  the  reducing  power  of  the  solu- 
tion is  liable  to  change. 

The  amount  of  reduction  of  the  copper  salt  to  the  cuprous 
oxide  is  afifected  by  the  rate  at  which  the  sugar  solution  is 
added,  the  time  and  degree  of  heating,  and  the  strength  of 
the  sugar  solution;  hence  the  necessity  for  adopting  a 
definite  procedure. 


food:     analytical    METHODS:     MILK.  IO3 

(b)  Graz'inwtrically  by  weighing  as  Cupric  Oxidc.^ 

Directions. — To  15  c.c.  of  the  copper  sulphate  solution  add 
15  c.c.  of  the  alkaline  tartrate  solution  in  a  150-c.c.  Erlen- 
meyer  flask.  Add  50  c.c.  of  freshly  boiled  distilled  water  and 
place  the  flask  in  a  boiling-water  bath  for  five  minutes.  Then 
from  a  calibrated  flask  quickly  add  25  c.c.  of  the  sugar  solu- 
tion to  the  hot  Fehling  liquor,  leave  the  25-c.c.  flask  inverted 
in  the  mouth  of  the  larger  one,  and  keep  the  whole  in  the 
boiling-water  bath  for  fifteen  minutes.  At  the  end  of  this 
time  remove  the  flask  and  filter  ofY  the  cuprous  oxide  as 
rapidly  as  possible  through  a  thick  layer  of  asbestos  in  a 
weighed  porcelain  Gooch  crucible.  Wash  with  boiling  dis- 
tilled water  until  the  wash-water  no  longer  reacts  alkaline. 
Place  the  crucible  in  a  platinum  or  nickel  crucible  and  heat  it, 
gently  at  first,  then  to  a  red  heat  for  about  fifteen  minutes. 
Cool  and  weigh  quickly,  as  the  cupric  oxide  is  somewhat 
hygroscopic.  Convert  the  weight  of  cupric  oxide  into  lactose 
by  multiplying  by  the  factor  0.6254,  which  will  be  sufficiently 
close  for  all  ordinary  work.  If  more  accurate  results  are  de- 
sired, consult  Defren's  table  in  the  article  previously  men- 
tioned. 

Notes. — The  asbestos  which  is  used  should  be  previously 
boiled  in  nitric  acid  and  then  in  dilute  sodium  hydroxide  and 
thoroughly  washed. 

The  amount  of  cuprous  oxide  produced  by  the  action  of 
one  gram  of  reducing  carbohydrate  on  Fehling's  solution,  in 
the  manner  described,  is  not  a  constant  for  all  dilutions.  For 
this  reason  the  amount  of  lactose  cannot  be  calculated  ex- 
actly from  the  weight  of  cupric  oxide,  but  reference  must  be 
made  to  the  specially  constructed  table.  Moreover,  each 
table,  whether  Allihn's,  Wein's,  or  Defren's,  can  be  used  only 


Defren:    TecA.  Quart.,  10  [iSgy),  167. 


t64  air.  water,  and  food. 

when  the  reduction  is  carried  out  under  conditions  similar  to 
those  employed  in  the  determinations  on  which  the  table  was 
based. 

(2)  Determination  by  the  Saccharimeter.  —  For  the 
optical  determination  of  milk-sugar  the  method  of  double  di- 
lution, as  described  by  Wiley  and  Ewell,*  will  be  found  satis- 
factory. 

Directions. — Into  each  of  two  flasks,  marked  at  100  and 
200  c.c,  respectively,  put  65.52  grams  of  milk,  add  10  c.c.  of 
acid  mercuric  nitrate,  fill  to  the  mark,  and  mix  by  shaking. 
Filter  through  dry  filters  and  polarize  in  a  400-millimeter 
tube,  using  the  Schmidt  and  Haensch  saccharimeter.  Cal- 
culate the  results  as  in  the  following  example: 

Weight  of  milk  used  =  65.52  grams; 

Reading  from  loo-c.c.  flask  =  20°. 84; 
"  "      200-c.c.  flask  =  10°.  15. 

Then  10. 15  X  2  =  20.30; 

20.84  —  20.30  =  0.54; 
0.54  X  2  =  1.08; 

20.84  —  1.08     =  19.76; 
19.76  -i-  4  =  4-94>  which  is  the  per  cent, 

of  milk-sugar. 

Notes. — The  object  in  using  the  method  of  double  dilu- 
tion is  to  avoid  the  necessity  of  making  corrections  for  the 
volume  of  the  precipitate  of  casein  and  fat.  The  method  is 
based  on  the  fact  that,  within  certain  limits,  the  polarizations 
of  two  solutions  of  the  same  substance  are  inversely  propor- 
tional to  their  volumes. 

The  flasks  should  be  filled  at  nearly  the  same  temperature 
as  that  at  which  the  polarizations  are  made,  and  the  tem- 

*  Analyst,  21   {/S<p6),  183. 


food:   analytical  methods:   milk.  165 

perature  of  the  room  should  be  kept  as  nearly  as  possible  at 
20°  to  avoid  errors  arising  from  marked  changes  in  tempera- 
ture. 

PROTEIDS  OF  milk. 

Determination  of  Total  Proteids. — Weigh  5  grams  of 
milk  into  a  750-c.c.  round-bottomed  tiask  and  determine  the 
nitrogen  by  the  Kjeldahl  process  as  directed  on  page  183. 
IMultiply  the  per  cent,  of  nitrogen  by  the  factor  6,25  to  obtain 
the  per  cent,  of  proteids. 

Separation  of  Casein  and  Albumin.*  —  Directions.  — 
To  5  grams  of  milk  add  50  c.c.  of  a  solution  of  magnesium 
sulphate  (saturated,  at  40°-50°)  and  heat  the  mixture  to 
about  45°  until  the  precipitate  settles  out,  leaving  the  super- 
natant liquid  clear.  Filter  and  wash  the  precipitate  several 
times  with  the  solution  of  magnesium  sulphate  prepared  as 
above,  keeping  the  temperature  at  about  45°.  Determine  the 
nitrogen  in  this  precipitate  and  multiply  by  6.38  for  the  casein. 
The  difference  between  the  total  and  casein  nitrogen  will  be 
the  amount  corresponding  to  the  albumin,  together  with  the 
very  small  amount  of  globulin. 

Notes. — The  principal  proteid  body  present  in  milk  is 
casein.  Others  present  in  much  smaller  quantity  are  albumin, 
peptone,  and  fibrin  or  globulin.  Different  observers  at  vari- 
ous times  have  claimed  the  presence  of  other  nitrogenous 
bodies,  but  these  have  not  been  entirely  substantiated. 

It  is  now  generally  held  that  the  colloidal  state  in  which 
the  casein  is  held  in  milk  is  due  to  the  combination  with  it  of 
certain  mineral  compounds,  chiefly  those  of  calcium.  The 
action  of  precipitants  is  on  these  mineral  matters,  breaking 
up  the  combination  and  releasing  the  insoluble  casein. 

Sebelien:  Ztschr.  physiol.  Cheni.,  13  (i88g),  160. 


l66  AIR,    WATER,    AND    FOOD. 

Most  authorities  at  present  favor  the  factor  6.38  for  cal- 
culating the  casein,  although  the  old  factor  6.25  is  still  largely 
used. 

Adulterants. — The  most  common  forms  of  adulteration 
of  milk  are  the  addition  of  water  and  the  removal  of  cream. 
The  former  is  detected  by  the  decrease  in  the  specific  gravity, 
total  solids  and  ash,  and  the  latter  by  the  increased  specific 
gravity  and  greatly  decreased  amount  of  fat.  Various  sub- 
stances may  also  be  added,  such  as  salt,  cane-sugar,  or  starch. 

Direct  Determination  of  Added  Water. — This  is  best  done 
by  determining  the  specific  gravity  of  the  milk-scrum  after 
coagulation  and  removal  of  the  casein.*  The  casein  is  co- 
agulated by  dilute  acetic  acid,  filtered  of?  on  a  dry  filter,  and 
the  specific  gravity  of  the  filtrate  taken  at  15°  C.  by  the  West- 
phal  balance.  The  specific  gravity  of  the  serum  from  normal 
milk  is  never  below  1.027  ^^''^  only  rarely  below  1.029.  The 
addition  of  each  ten  per  cent,  of  water  lowers  the  specific 
gravity  by  0.00 10  to  0.0035. 

Salt. — Detected  by  the  high  percentage  of  ash  and  deter- 
mined by  titration  with  silver  nitrate  and  potassium  chromate 
either  in  the  ash  or  in  the  milk  itself  after  clarification  with 
milk  of  alumina. 

Cane-sugar. — To  detect  the  presence  of  cane-sugar  boil 
about  10  c.c.  of  the  milk  with  o.i  gram  of  resorcin  and  i  c.c. 
of  hvdrochloric  acid  for  five  minutes.  The  liquid  will  be  col- 
ored rose-red  if  cane-sugar  be  present.  The  quantitative  de- 
termination may  be  made  by  means  of  the  polariscope. 

Starch. — Heat  10  c.c.  of  the  milk  to  boiling  in  a  test-tube, 
and  when  cold  add  a  few  drops  of  a  solution  of  iodine  in  po- 
tassium iodide.  The  presence  of  even  0.2  per  cent,  of  starch 
will  be  shown  by  the  characteristic  blue  coloration. 

*  Woodman:  /.  Am.  Chem.  Soc,  21  {i8gg),  503. 


food:    analytical  methods:    milk.  167 

Coloring-matters.*  —  The  principal  coloring-matters 
added  to  milk  are  annatto,  caramel,  and  aniline  dyes.  In 
general,  coloring-matters  are  added  only  to  watered  milk,  but 
occasionally  samples  which  were  of  standard  quality  have 
been  found  to  be  colored. 

Directions. — Put  about  100  c.c.  of  the  milk  into  a  small 
beaker,  add  2  c.c.  of  25  per  cent,  acetic  acid  and  allow  the 
beaker  to  stand  cjuietly  for  about  ten  or  fifteen  minutes  in  a 
water-bath  kept  at  70°  C,  the  casein  being  thus  separated  as 
a  compact  cake.  Decant  off  the  whey,  squeezing  the  curd  as 
free  from  it  as  possible  by  means  of  a  spatula.  Transfer  the 
curd  to  a  flask  and  let  it  remain  covered  with  ether  for  an  hour 
or  more. 

Evaporate  the  ether  extract  which  contains  the  annatto 
if  present,  take  up  the  residue  with  water  made  faintly  alka- 
line with  sodium  hydroxide  and  filter  through  a  wet  filter.  If 
annatto  is  present,  it  will  permeate  the  filter  and  give  it  an 
orange  color  when  the  fat  is  washed  off  and  the  filter  dried. 
Treat  the  dried  filter  with  stannous  chloride.  If  annatto  is 
present,  a  pink  color  will  be  produced. 

After  pouring  off  the  ether  examine  the  milk-curd  for 
caramel  or  aniline  orange.  If  the  curd  is  left  white,  neither 
of  these  colors  is  present.  If  caramel  has  been  used,  the  curd 
will  be  of  a  pinkish-brown  color;  if  the  color  is  due  to  the 
aniline  dye,  the  curd  will  have  a  yellow  or  orange  tint.  To 
distinguish  between  the  two  colors  shake  a  small  portion  of 
the  curd  in  a  test-tube  with  strong  hydrochloric  acid.  The 
caramel-colored  curd  will  act  similarly  to  an  uncolored  curd, 
that  is,  it  will  gradually  produce  a  deep  blue  color  in  the  so- 
lution. On  the  other  hand,  the  aniline  color  will  immediately 
produce  with  the  hydrochloric  acid  a  pink  color. 

*  Ann.  Rep.  State  Bd.  Health,  Mass.,  1898,  697. 


1 68  AIR.    NVATKR,    AND    FOOD. 

Preservatives. — The  preservatives  usually  added  to  milk 
are  salicylic  acid,  borax  or  boric  acid,  formaldehyde,  and 
occasionally  benzoic  acid  and  potassium  chromate.  Car- 
bonate of  soda  is  also  added  in  some  cases  to  disguise  the 
acidity  of  sour  milk. 

Salicylic  Acid. — To  50  c.c.  of  the  milk  add  10  c.c.  of  the 
acid  mercuric  nitrate  used  in  the  optical  determination  of 
milk-sugar,  shake  and  filter.  Shake  the  filtrate  violently  in 
a  separatory  funnel  with  30  c.c.  of  a  mixture  of  equal  parts 
of  ether  and  petroleum  ether.  Evaporate  the  ethereal  solu- 
tion to  dryness  and  add  a  drop  of  neutral  ferric  chloride 
solution  to  the  residue.  If  salicylic  acid  is  present,  the  char- 
acteristic violet  color  will  be  produced. 

Boric  Acid. — Add  5  drops  calcium  hydroxide  solution  to 
10  (or  100)  c.c.  of  milk  and  evaporate  to  dryness  on  a  water- 
bath.  Char  the  residue,  add  2  c.c.  water  and  a  few  drops  of 
dilute  hydrochloric  acid,  and  filter  into  a  porcelain  dish. 
Test  the  filtrate  in  the  usual  way  with  turmeric-paper  or  by 
the  alcohol-fiame  test.  For  the  latter  methyl  alcohol  is  best. 
The  tests  for  l)oric  acid  can  also  be  applied  to  the  hydro- 
chloric acid  solution  of  the  ash. 

Formaldehyde. — This  is  generally  used  as  a  40  per  cent, 
aqueous  solution,  sold  under  the  name  of  formalin.  Several 
simple  tests  commonly  used  for  the  presence  of  formaldehyde 
will  be  described. 

(i)  When  the  sulphuric  acid  is  added  to  the  milk  in  mak- 
ing the  Babcock  test  for  fat,  a  bluish-violet  ring  will  be 
noticed  at  the  junction  of  the  two  liquids  when  formaldehyde 
is  present.  One  part  of  formaldehyde  in  200,000  parts  of 
milk  can  be  detected  by  this  test,  but  it  fails  when  the  for- 
maldehyde amounts  to  0.5  per  cent.  The  test  is  more 
delicate  if  the  sulphuric  acid  contains  a  trace  of  ferric  chlo- 
ride. 


food:     analytical    METHODS:     BUTTER.  1 69 

(2)  To  10  c.c.  of  milk  add  i  c.c,  of  fuchsin  sulphurous 
acid  and  allow  it  to  stand  five  minutes;  it  takes  on  a  pink 
color  whether  formaldehyde  be  present  or  not.  Then  add  J 
c.c.  of  dilute  hydrochloric  acid  and  shake.  Pure  milk  be- 
comes yellowish  white,  while  milk  containing  formaldehyde 
gives  a  violet  color.  This  test  will  detect  i  part  of  formalde- 
hyde in  20,000  parts  of  milk,  and  if  applied  to  the  distillate 
from  the  milk  will  show  i  part  in  500,000. 

(3)  To  10  c.c.  of  milk  in  a  small  porcelain  dish  add  an 
equal  volume  of  hydrochloric  acid  (1.12  sp.  gr.).  Add  one 
drop  of  ferric  chloride  solution  and  heat  the  dish  with  a  small 
flame,  stirring  vigorously,  until  the  contents  are  nearly  boil- 
ing. Remove  the  flame  and  continue  the  stirring  for  two 
or  three  minutes.  The  presence  of  formaldehyde  will  be 
shown  by  a  violet  color  which  appears  in  the  particles  of  the 
precipitated  casein,  the  depth  of  color  depending  on  the 
amount  of  formaldehyde  present.  This  test  readily  shows 
the  presence  of  i  part  of  formaldehyde  in  500,000  parts  of 
milk. 

Benzoic  Acid. — Fres.  Zcit.,  21,  531;  Jour.  Anal.  Chem.,  2,. 
446. 

Sodium  Carbonate. — Detected  in  the  milk-ash,  as  on 
page  153.  If  effervescence  occurs,  test  the  original  milk  with 
rosolic  acid  as  follows:  Mix  10  c.c.  of  milk  with  an  equal 
volume  of  alcohol,  and  add  a  few  drops  of  a  one  per  cent, 
solution  of  rosolic  acid.  The  presence  of  sodium  carbonate 
is  indicated  by  a  more  or  less  distinct  pink  coloration.  A 
comparative  test  should  be  made  at  the  same  time  with  milk 
known  to  be  pure. 

BUTTER. 

General  Statements. — Butter  consists  of  the  fat  of  milk,  to- 
gether with  a  small   percentage   of  water,   salt,  and   curd. 


170  ATR,    WATER,    AND    FOOD. 

The  curd  is  made  up  principally  of  the  casein  of  the  milk. 
These  various  ingredients  are  present  in  about  the  following 
proportions: 

Fat 78.00-90  o  per  cent. ;  average,  82  per  cent. 

Water 5.00-20.0   "        "  "         12 

Salt 0.40-15.0    "       "  "  5 

Curd o.n-  5-3    "        "  "  ^ 

The  fat  consists  of  a  mixture  of  the  glycerides  of  the  fatty 
acids.  The  characteristic  feature  of  butter-fat  is  the  extraor- 
dinarily high  proportion  of  the  glycerides  of  the  soluble  and 
volatile  fatty  acids  when  contrasted  with  other  fats. 

Recent  investigations  *  show  the  following  to  be  the 
probable  composition  of  normal  butter-fat: 

Acid.  Per  cent.  Acid.        Per  cent.  Triglycerides. 

Dioxystearic i-oo  1.04 

Oleic 32.50  33-95 

Stearic 1-83  i-9i 

Palmitic 38.61  40.51 

Myristic 9-89  10.44 

Laurie 2.57  2.73 

Capric ;••••     0.32  0.34 

Caprylic 0.49  0.53 

Caproic 2.09  2.32 

Butyric 5-45  6.23 

Total 94-75  100.00 

According  to  this,  the  proportion  of  volatile  acids  in  but- 
ter (butyric,  caproic^  caprylic,  and  capric  acids)  amounts  to 
^•35  per  cent.  The  amount  of  volatile  acid  in  lard,  for  ex- 
ample, is  about  0.1  per  cent. 

The  usual  examination  of  butter  consists  in  the  examina- 
tion of  the  butter-fat,  in  order  to  detect  the  presence  of  foreign 
fats.  The  determination  of  the  amount  of  curd  may  be  of 
value  also  in  some  cases,  more  especially  from  a  sanitary 

*  Browne:  /.  Am.  Chem.  Soc,  21  (rSgg),  807. 


food:     analytical    METHODS:    BUTTER.  I/I 

Standpoint.  The  chief  danger  to  health  probably  lies  in  the 
possible  decomposition  of  the  nitrogenous  portion,  for  it  is 
•quite  generally  recognized  that  the  substitution  of  oleo- 
margarine is  not  injurious  to  health.  It  is  a  not  infrequent 
practice,  however,  as  remarked  in  the  previous  chapter,  to 
incorporate  a  large  amount  (sometimes  as  high  as  33  per 
cent.)  of  curd  and  other  nitrogenous  matters  in  fresh  butter. 
If  this  is  kept  for  any  length  of  time,  a  decomposition  is 
liable  to  occur  which  may  have  serious  effects.  Other  de- 
terminations that  are  usually  made  are  the  water  and  salt. 

The  "  aroma  "  of  butter  seems  to  be  connected  with  the 
decomposition  produced  by  the  action  of  bacteria  on  the 
casein  and  the  small  amount  of  milk-sugar  that  is  present, 
and  not  with  any  change  in  the  fats;  there  is  no  evidence, 
however,  that  any  unwholesome  effect  is  produced  by  the 
aroma-giving  organisms. 

The  rancidity  of  butter-fat  is  generally  considered  to  be 
due  to  decomposition  and  oxidation  of  the  fatty  acids,  espe- 
cially the  unsaturated  ones,  the  amount  of  change  depending 
on  conditions  of  light,  heat,  and  exposure  to  air. 

Examination  of  the  Fat.  —  The  fat  is  first  separated 
from  the  other  constituents  of  the  butter  so  that  it  may  be 
weighed  out  for  the  various  tests. 

Directions. — Melt  a  piece  of  butter,  about  two  cubic 
inches,  in  a  small  beaker  placed  on  top  of  the  water-bath  so 
that  the  temperature  shall  not  rise  above  50°-6o°.  After 
about  fifteen  minutes  the  water,  salt,  and  curd  will  have  set- 
tled to  the  bottom.  (A  better  separation  may  be  secured 
by  pouring  the  melted  butter  into  a  test-tube  and  whirling 
it  for  3-4  minutes  in  a  centrifugal  machine.)  Place  a  bit  of 
absorbent  cotton  in  a  funnel,  previously  warmed,  and  decant 
ofT  the  clear  fat  through  the  cotton  into  a  second  I)caker, 
taking  care  that  none  of  the  water  or  curd  is  brought  upon 


172  AIR,    WATKK,    AND    FOOD. 

the  filter.     When  the  fihered  fat  has  cooled  to  about  40** 
place  a  small  pipette  in  the  beaker  and  weigh  the  whole. 

By  means  of  the  pipette  the  desired  amount  of  fat  is  taken 
out,  the  pipette  replaced  in  the  beaker,  and  the  whole  again 
weighed.  The  difference  in  weight  gives  the  exact  amount 
of  fat  taken.  It  is  a  saving  of  time,  however,  if  several  por- 
tions are  to  be  weighed  out,  to  make  the  weights  one  after 
another,  so  that  one  weight  will  suf^ce  for  a  determination. 
Weigh  out  thus:  Two  portions  of  5  grams  each  into  250-c.c. 
round-bottomed  flasks  for  the  Reichert-Meissl  method,  one 
portion  of  2.5  to  3  grams  into  a  500-c.c.  beaker  for  Hehner's 
process,  tw'o  portions  of  about  i  gram  each  into  300-c.c» 
glass-stoppered  bottles  fo;  Hiibl's  process. 

(i)  Reichert-Meissl  Number  for  Volatile  Fatty  Acids. 
— Directions. — To  the  fat  in  the  250-c.c.  flasks  add  2  c.c.  of 
strong  caustic  potash  (1:1)  and  10  c.c.  of  95  per  cent, 
alcohol.  Connect  the  flask  with  a  return-flow  condenser 
and  heat  on  a  water-bath  so  that  the  alcohol  boils  vigorously 
for  25  minutes.  At  the  end  of  this  time  disconnect  the  flask 
and  evaporate  ofif  the  alcohol  on  a  boiling-water  bath.  After 
the  complete  removal  of  the  alcohol  add  140  c.c.  of  re- 
cently boiled  distilled  water  wdiich  has  been  cooled  to  about 
50°.  The  water  should  be  added  slowly,  a  few  cubic  centi- 
meters at  a  time.  Warm  the  flask  on  the  water-bath  until 
a  clear  solution  of  the  soap  is  obtained.  Cool  the  solution  to 
about  60°  and  add  8  c.c.  of  sulphuric  acid  (1:4)  to  set  free 
the  fatty  acids.  Drop  two  bits  of  pumice,  about  the  size  of 
a  pea,  into  the  flask,  close  it  by  a  well-fitting  cork,  w'hich  is 
tied  in  with  twine,  and  immerse  it  in  boiling  water  until  the 
fatty  acids  have  melted  to  an  oily  layer  floating  on  the  top 
of  the  liquid.  Cool  the  flask  to  about  60°,  remove  the  cork, 
and  immediately  attach  the  flask  to  the  condenser. 

Distil  no  c.c.  into  a  graduated  flask  in  as  nearly  thirty 


food:    analytical  methods:    butter.  173 

ininiites  as  possible.     Thoroughly  mix  the  distillate,  pour  the 

whole  of  it  through  a  dry  filter,  and  titrate  100  c.c.  of  the 

N 
mixed  filtrate  with   — ■     sodium    hydroxide,    using    phenol- 

phthalein  as  an  indicator.  Increase  the  number  of  cubic  centi- 
meters of  alkali  used  by  one-tenth,  and  correct  the  reading 
also  for  any  weight  of  fat  greater  or  less  than  5  grams. 

For  example,  if  5.3  grams  of  butter-fat  are  used,  and  100 

N 
c.c.  of  the  distillate  require  27.4  c.c.  of  —•  NaOH,  no  c.c. 

would  require  27.4  +  2.74  =  30.14  c.c.  Then  5.3  :  30.14  = 
^  :  X.  X  =  28.4.  X  is  the  Reichert-Meissl  number. 

Notes. — The  Reichert-Meissl  number  for  genuine  butter 
varies  from  24  to  34;  the  average  usually  taken  is  28.8. 
Oleomargarine  gives  a  number  of  about  1.5  to  2. 

When  the  fat  is  treated  with  potash  it  is  decomposed,  the 
glycerine  being  set  free,  and  the  potassium  salts  of  the  fatty 
acids,  that  is  to  say.  the  potassium  soaps  are  formed.  Hence 
the  process  is  called  saponification.  For  butyric  acid  the  re- 
action is 

C3H,(C3H,COO)3  -f  3KOH  =  sCaH^COOK  -f  C3H,(OH)3. 

The  alcohol  is  used  to  dissolve  the  fat.  But  at  the 
moment  the  butyric  acid  is  set  free  it  tends  to  combine  with 
the  alcohol  to  form  a  volatile  ether: 

C3H7COOH  +  C2H5OH  =  QH..COOC2H5  -f  H2O. 

The  object  of  the  return-f^ow  condenser  is  to  prevent  the 
escape  of  this  volatile  ether  and  to  allow  of  its  complete 
saponification. 

If  the  .water  used  to  dissolve  the  soap  is  added  too  rap- 
idly, the  soap  may  be  decomposed  with  the  liberation  of  the 
fatty  acids:  C3H7  COOK  +  H2O  =  QH^  COOH  +  KOH. 


174  AIR,    WATER,    AND    FOOD. 

The  fatty  acids  are  set  free  at  the  proper  time  by  means 
of  sulphuric  acid,  and  the  volatile  acids  distilled  off  and 
titrated.     The  pumice  is  added  to  prevent  explosive  boiling. 

The  whole  of  the  volatile  acids  do  not  pass  over  into  the 
distillate,  but  only  a  part,  the  amount  depending  upon  the 
rate  of  distillation  and  the  volume  of  the  distillate.  Hence,  in 
order  to  get  uniform  results,  it  is  necessary  to  follow  the  pre- 
scribed procedure  with  great  care. 

(la)  Method  of  Leffman  and  Beam.  —  In  order  io 
shorten  the  time  required  for  the  saponification  and  subse- 
quent removal  of  the  alcohol,  Leffman  and  Beam  *  have 
proposed  the  use  of  a  solution  of  sodium  hydroxide  in  glycer- 
ine as  the  saponifying  agent. 

Directions. — To  the  fat,  weighed  out  into  a  250-c.c.  flask, 
as  in  the  Reichert-Meissl  method,  add  20  c.c.  of  the  glycerine- 
soda  solution  and  heat  the  flask  over  a  lamp.  Boil  the  mix- 
ture gently  until  all  the  water  has  been  driven  off  and  the 
liquid  becomes  perfectly  clear,  which  will  usually  be  the  case 
in  about  five  minutes.  Care  should  be  taken  to  avoid  loss 
from  spattering.  Allow  the  flask  to  cool  somewhat,  and 
dissolve  the  soap  in  135  c.c.  of  boiled  distilled  water.  Add 
the  first  portions  of  water  drop  1)y  drop,  shaking  the  flask 
each  time  to  avoid  foaming.  When  the  soap  is  dissolved, 
add  5  c.c.  of  sulphuric  acid  (1:4),  two  pieces  of  pumice,  and 
carry  out  the  distillation  without  previous  melting  of  the 
fatty  acids.  The  distillation  and  titration  are  completed  as 
in  the  Reichert-Meissl  process. 

(2)  Hehner's  Method  for  Direct  Determination  of 
the  Fixed  Fatty  Acids.  —  Directions. — To  the  portion  of 
2.5  grams  weighed  out  into  the  500-c.c.  beaker  add  i  c.c.  of 
caustic  potash  and  20  c.c.  of  95  per  cent,  alcohol.     Cover 

*  "Analysis  of  Milk  and  Milk  Products"  (Philadelphia,  1896).  p.  78. 


food:     analytical    METHODS:     BUTTER.  175 

the  beaker  with  a  watch-glass  and  heat  it  on  the  water-bath 
until  the  liquid  is  clear  and  homogeneous.  As  it  is  not 
essential  to  prevent  the  escape  of  the  volatile  acids,  the  use 
of  a  return-flow  condenser  is  not  necessary.  Evaporate  off 
the  alcohol  on  the  water-bath  and  dissolve  the  soap  in  about 
400  c.c.  of  warm  distilled  water.  When  the  soap  is  com- 
pletely dissolved  add  10  c.c.  of  hydrochloric  acid  (sp.  gr. 
1. 12),  and  heat  the  beaker  in  the  water-bath  almost  to  boil- 
ing until  the  clear  oil  floats.  Meanwhile  dry  and  weigh  a 
thick  filter  in  a  small  covered  beaker.  Allow  the  solution  to 
cool  until  the  fat  forms  a  solid  cake  on  top;  filter  the  clear 
liquid  and  finally  bring  the  solid  fats  upon  the  weighed  filter. 
Wash  the  beaker  and  fat  thoroughly  with  cold  water,  then 
wash  out  the  fat  adhering  to  the  beaker  with  boiling  water, 
which  is  poured  through  the  filter,  taking  care  that  the  filter 
is  never  more  than  two-thirds  full.  Cool  the  funnel  by 
plunging  it  into  cold  water,  remove  the  filter,  place  it  in  the 
weighing-beaker  and  dry  it  at  100°  to  constant  weight.  The 
fat  should  be  heated  about  an  hour  at  first,  then  for  periods 
of  about  fifteen  minutes,  until  the  weight  is  constant  within 
2  mgs. 

N'otes. — 87.5  per  cent,  is  usually  taken  as  the  proportion 
of  fixed  fatty  acids  in  butter-fat;  88  and  89  per  cent,  have 
been  frequently  found.  All  other  fats  yield  from  95  to  96 
per  cent,  of  insoluble  fatty  acids. 

(3)    Method   of  Baron    Hiibl. — This  method  is  based  on 
the  fact  that  certain  of  the  fatty  acids,  notably  the  "  unsatu- 
rated acids,"  as  oleic  acid,  C17H33COOH,  take  up  the  halo 
gens  with  the  formation  of  addition  products. 

Directions. — Dissolve  the  butter-fat  in  the  300-c.c.  bottles 
in  10  c.c.  of  dry  chloroform.  Add  30  c.c. — in  the  case  of  a 
doubtful  butter  50  c.c. — of  the  iodo-mercuric  solution  from 
a  pipette  or  glass-stoppered  burette,  and  allow  the  bottles  to 


176  AIR,    WATER,    AND    FOOD. 

Stand,  with  frequent  shaking,  for  three  hours  in  a  dark  closet. 
A  blank  should  be  carried  through  at  the  same  time  and  with 
the  same  amount  of  reagents,  in  order  to  determine  the  rela- 
tion between  the  thiosulphate  and  the  iodo-mercuric  solu- 
tion, the  latter  being  liable  to  change.  Now  add  20  c.c.  of 
potassium  iodide  (to  prevent  precipitation  of  mercuric  iodide 
on  dilution),  then  100  c.c.  of  distilled  water,  and  titrate  the 

excess  of  iodine  with  —  sodium  Tliiosulphate  until  the  solu- 
10  ^ 

tion  is  faintly  yellow.  Add  a  few  drops  of  starch  solution 
and  titrate  to  the  disappearance  of  the  blue  color.  Calculate 
the  result  in  grams  of  iodine  absorbed  by  100  grams  of  fat. 
This  is  called  the  Hiibl  or  Iodine  absorption-number. 

Standardization  of  the  Thiosulphate  Solution. — As  this  is 
not  permanent,  its  strength  should  be  determined  by  means 
of  the  standard  potassium  bichromate  solution,  i  c.c.  of 
which  is  equivalent  to  o.oi  gram  of  iodine.  The  standardi- 
zation may  be  done  while  waiting  for  the  absorption  of  the 
iodine. 

Measure  20  c.c.  of  the  potassium  bichromate  from  a  pipette 
into  an  Erlenmeyer  fiask.  Add  10  c.c.  of  potassium  iodide, 
100  c.c.  of  water,  and  5  c.c.  of  strong  hydrochloric  acid,  and 
shake  the  flask  for  three  minutes.  Titrate  the  liberated 
iodine  with  the  thiosulphate  solution  until  the  color  has 
almost  disappeared,  then  add  starch  solution  and  continue  the 
titration  until  the  blue  color  changes  to  a  sea-green,  due  to 
the  formation  of  chromium  chloride.  The  iodine  is  liberated 
in  accordance  with  the  following  equation: 

KoCr.O^  +  14HCI  +  6KI  =  8KC1  +  2Cra3  -f  7H0O  +  61. 

Calculation  of  Results. — Example. — From  the  standardi- 
za*:ion. 


food:     analytical   METHODS:     BUTTER.  1 77 

17.2  c.c.  thiosulphate  =  21.5  c.c.  bichromate  =  0.215  gram  I; 

I  c.c.  thiosulphate  =  0.0125  gram  I. 

Also,  from  blank, 

31  c.c.  iodine  solution  =  46.5  c.c.  thiosulphate; 
I   c.c.  iodine  solution  ^    1.5  c.c.  thiosulphate. 

If  31  c.c.  iodine  solution  have  been  added  to  1.049  grams 

of  fat,  then  31.0  X  1.5  =  46.5  c.c.  is  the  equivalent  amount 

of  thiosulphate  solution;  and  if  19,4  c.c.  thiosulphate  were 

used  to  titrate  excess  of  free  iodine,  46.5  —  19.4  =  27.1  c.c.  is 

the  amount  of  thiosulphate  equivalent  to  the  iodine  combined 

with  the  fat.     Then,  since  i  c.c.  thiosulphate  is  equivalent  to 

,       .    ,.       27.1  X  0.0125  .  . 
0.0125  gram  free  lodme,  — X  100  =  32.29  grams 

of  iodine  combined  with  100  grams  fat. 

Notes. — It  is  assumed  that  106  grams  of  pure  butter-fat 
absorb  30-40  grams  iodine;  artificial  butter,  55  grams;  oleo- 
margarine, 63-75  grams;  olive-oil,  83  grams;  and  cottonseed- 
oil,  106  grams. 

The  products  formed  by  the  action  of  iodine  on  the  fats 
are  mainly  addition  products  with  a  slight  proportion  of  sub- 
stituted bodies.  Thus  the  unsaturated  olein,  (€171133000)3 
C3H5,  takes  up  six  atoms  of  iodine,  forming  an  addition 
product,  di-iodo-stearin,  (C,7H33loCOO)3C3H5. 

The  exact  amount  of  iodine  absorbed  depends  on  the 
strength  and  the  amount  of  iodine  solution  used,  and  on  the 
length  of  time  it  is  allowed  to  act.  The  presence  of  mer- 
curic chloride  shortens  the  time  of  reaction,  probably  by 
acting  as  a  carrier  of  iodine. 

Physical  Methods. —  Microscopic  Examination.  —  Pure, 
fresh  butter  is  not  ordinarily  crystalline  in  structure.  Butter 
which  has  been  melted,  however,  and  fats  which  have  been 
liquefied  and  allowed  to  cool  slowly  show  a  distinct  crystal- 
line structure,  especially  by  polarized  light.    If  only  fresh  but- 


l/S  AIR,    WATER,    AND    FOOD. 

ter  were  sold,  and  all  adulterants  had  been  previously  melted 
and  slowly  cooled,  this  method  would  be  all  that  would  be 
necessary  for  the  detection  of  adulteration.  As  it  is,  how- 
ever, it  is  most  useful  in  making  comparative  examina- 
tions of  samples  which  have  been  subjected  to  the  same 
conditions.  From  an  examination  of  the  accompanying 
plate,*  which  shows  the  appearance  by  polarized  light  of 
four  samples  of  known  origin  which  were  melted  and  cooled 
slowly  under  exactly  similar  conditions,  it  will  be  seen  that, 
while  the  differences  are  noticeable,  they  are  not  sufficient  in 
all  cases  to  form  a  basis  for  absolute  identification. 

For  a  further  discussion  of  this  point  the  student  is  re- 
ferred to  Bulletin  13,  U.  S.  Dept.  Agr.,  Part  I,  pp.  29-40; 
Part  IV,  pp.  449-455- 

Specific  Gravity. — This  is  most  conveniently  determined 
at  100°  C.  by  means  of  the  Westphal  balance  (see  Allen,  The 
Amlyst,  II,  223;  also  Bull  13,  Part  IV,  pp.  430-431).  The 
pyknometer  method  is,  however,  the  one  adopted  by  the  As- 
sociation of  Official  Agricultural  Ghemists,  to  whose  report 
(Bulletin  46,   Rev.  Ed.,  1899,  p.  51)  reference  is  made. 

Melting-point. — This  is  best  determined  according  to  the 
directions  given  in  the  Bulletin  just  mentioned  (46),  p.  52. 

Refractive  Index. — The  degree  to  which  light  is  refracted 
differs  with  various  fats,  and  these  differences  are  often  of 
considerable  analytical  value.  See  Bulletin  46,  Rev.  Ed.,  p. 
49,  for  a  description  of  the  method  employed  in  its  determina- 
tion. 

Determination  of  Water.  —  Directions.  —  Weigh  2 
grams  of  butter  into  a  shallow  platinum  dish  having  a  flat 
bottom  two  inches  in  diameter  and  containing  a  slender  stir- 
ring-rod two  and  a  half  inches  long.  Heat  the  butter  in  the 
oven  at  100°  C.  for  thirty  minutes,  cool  in  a  desiccator,  and 

*  From  photomicrographs  by  A.  G.  Woodman  and  A.  I.  Kendall,  1900. 


A.    Kut'er  X  30. 

C.   Oleomargarine  X  30. 


K.    Reef-fat  X  3c 
U.    Lard  X  30. 


food:   analytical  methods:    butter.  i8r 

weigh.  Heat  again  for  periods  of  fifteen  minutes,  until  the 
weight  remains  constant.  During  the  process  of  heating 
stir  the  butter  frequently  to  hasten  evaporation  of  the  water. 

]S[ote. — The  loss  in  weight  is  calculated  as  water,  although 
a  portion  of  the  volatile  acids  is  also  lost,  the  amount  depend- 
ing upon  the  time  of  heating. 

Determination    of   Salt. — Directions. — Weigh  lo  grams 

of  butter  in  a  small  beaker,  add  30  c.c.  of  hot  water,  and 

when  the  fat  is  completely  melted  transfer  the  whole  to  a 

separatory   funnel.     Shake   the    mixture    thoroughly,    allow 

the  fat  to  rise  to  the  top,  and  draw  off  the  water,  taking  care 

that  none  of  the  fat-globules  pass  the  stopcock.     Repeat  the 

operation  four  times,  using  30  c.c.  of  water  each  time.    Make 

the  washings  up  to  250  c.c,  mix  thoroughly,  and  titrate  25 

N 
c.c.  in  a  six-inch  porcelain  dish,  using  —  silver  nitrate  with 

potassium  chromate  as  an  indicator. 

Complete  Analysis  of  Butter  in  One  Sample. — Direc- 
tions.— Weigh  about  2  grams  of  butter  into  a  platinum 
Gooch  crucible,  half-filled  with  ignited  fibrous  asbestos,  and 
dry  it  at  100°  C.  to  constant  weight.  The  loss  in  weight  is 
the  amount  of  luatcr.  Then  treat  the  crucible  repeatedly 
with  smah  portions  of  petroleum  ether,  using  gentle  suction, 
and  again  dry  it  to  constant  weight.  The  difference  between 
this  and  the  preceding  weight  will  be  the  amount  of  fot. 
Now  carefully  heat  the  crucible  over  a  small  flame  or  in  a 
muffle  until  a  light  grayish  ash  is  obtained.  The  loss  in 
weight  is  the  amount  of  curd,  and  the  residual  increase  in 
weight  over  that  of  the  crucible  and  asbestos  is  the  ash.  If  de- 
sired, the  salt  may  be  washed  out  of  the  ash  and  determined 
by  titration  w^ith  silver  nitrate. 

Detection  of  Coloring  -  matters. — The  principal  color- 
ing-matter used  in  butter  is  annatto;  sometimes  saffron  is 


1 82  AIR,    WATER,    AND    FOOD. 

employed.     These  may  be  detected  by  the  method  proposed 
by  Cornwall.* 

Directions. — Dissolve  about  5  grams  of  the  warm  filtered 
fat  in  50  c.c.  of  ether  and  shake  in  a  separatory  funnel  for 
ten  or  fifteen  seconds  with  15  c.c.  of  a  very  dilute  solution 
of  caustic  potash,  only  alkaline  enough  to  give  a  distinct  re- 
action with  turmeric-paper.  After  an  hour  or  two  draw  off 
the  aqueous  solution,  colored  more  or  less  by  the  annatto, 
shake  it  once  more  with  a  fresh  portion  of  ether,  and  evapo- 
rate to  dryness.  Treat  the  dry  residue  with  a  drop  of  con- 
centrated sulphuric  acid.  In  the  presence  of  annatto  the 
yellow  residue  turns  blue  or  violet,  then  quickly  green,  and 
finally  brownish  or  somewhat  violet.  Saffron  differs  in  not 
giving  the  green  coloration.  Blank  tests  should  be  made 
with  the  ether. 

FLOUR,  PREPARED  CEREALS,  ETC. 

This  class  of  foodstuffs  is  usually  in  a  dry  form  and  not 
liable  to  rapid  change  by  micro-organisms,  and  the  examina- 
tion consists  in  the  determination  of  their  "  food  value."  This 
may  require  a  simple  analytical  process,  as  in  the  case  of  the 
quantity  of  nitrogen  in  a  sample  of  "  gluten  "  sold  for  diabetic 
patients,  or  in  the  case  of  a  brand  of  flour  to  be  used  in  a  hos- 
pital or  State  institution.  It  may  also  require  an  estimation 
of  the  available  food-material,  as  in  the  case  of  two  kinds  of 
beans  or  corn.  The  actual  determination  of  digestibility  be- 
longs to  physiological  chemistry  and  need  not  be  taken  into 
consideration  here. 

Moisture.  —  Directions. — Spread  about  2  grams  of  the 
finely  ground  material  in  a  thin  layer  on  a  watch-glass  and 
dry  it  in  the  oven  at  100°  C.  for  five  hours. 

*  C^em.  Nezvs,  SS  {^SSy),  49. 


food;   analytical  methods:   cereals.  183 

Note. — With  some  substances  drying  in  a  current  of 
hydrogen  or  some  inert  gas  may  be  necessary,  but  for  most 
cereals  the  method  given  will  be  found  satisfactory. 

Ash. — Directions. — Weigh  about  2  grams  into  a  plati- 
num dish,  such  as  is  used  for  the  determination  of  water  in 
butter,  and  char  it  carefully.  Ignite  at  a  very  low  red  heat 
until  the  ash  is  white,  preferably  in  a  muffle  or  radiator. 

Note. — If  a  white  ash  cannot  be  obtained  in  this  manner, 
exhaust  the  charred  mass  with  water,  collect  the  insoluble 
residue  on  a  filter,  burn  it,  add  this  ash  to  the  residue  from 
the  evaporation  of  the  aqueous  extract  and  heat  the  whole  at 
a  low  red  heat  until  the  ash  is  white. 

Ether  Extract  :  Fats  and  Oils.— Directions. — Place  the 
residue  from  the  determination  of  moisture,  as  described 
above,  in  an  extraction-cone  and  extract  it  with  pure  anhy- 
drous ether  for  sixteen  hours.  Evaporate  o^  the  ether  and 
dry  the  residual  fat  at  a  low  tem.perature  to  constant  weight. 

Total  Proteids  :  Determination  of  Nitrogen  by  the 
Kjeldahl  Process.* — Principle. — Oxidation  of  carbon  and 
hydrogen,  and  conversion  of  organic  nitrogen  to  ammonium 
sulphate  by  means  of  boiling  sulphuric  acid  in  presence  of 
mercury,  the  latter  acting  as  a  carrier  of  oxygen,  and  being 
converted  to  mercuric  sulphate.  Precipitation  of  mercury  by 
potassium  sulphide  to  prevent  the  formation  of  mercur- 
ammonium  compounds  when  the  solution  is  made  alkaline. 
Setting  free  of  ammonia  by  neutralization  of  the  acid  by  po- 
tassium hydroxide.    Distillation  of  ammonia  into  a  measured 

N 
quantity  of  — -  hydrochloric  acid.    Titration  of  excess  of  acid. 

Directions. — Transfer  about  0.5  gram  of  the  finely  divided 
substance  from  a  weighing-tube  to  a  750-c.c.  round-bot- 
tomed flask,  add  10  c.c.  of  concentrated  sulphuric  acid  free 

*  Ztschr.  anal.  Chem.,  22  {rSSj),  366. 


184  AIR,    WATER,    AND    FOOD. 

from  nitrogen,  and  0.2  gram  of  metallic  mercury.  Place  a 
small  funnel  in  the  neck  of  the  fiask,  which  should  be  sup- 
ported in  an  inclined  position  on  wire  gauze  and  heated  with 
a  small  flame  until  frothing  has  ceased  and  the  liquid  boils 
quietly.  Then  increase  the  heat  and  boil  the  solution  for  half 
an  hour  after  it  becomes  colorless.  Allow  the  flask  to  cool 
for  a  minute  or  two,  and  add  a  few  crystals  of  potassium  per- 
manganate until  the  liquid  has  acquired  a  slight  green  or 
purple  color.  Meanwhile  free  the  distilling  apparatus  from 
ammonia  by  distillation  with  pure  water  until  a  slight  color 
only  is  given  to  50  c.c.  of  the  distillate  by  Nessler's  reagent. 

N 

]\Ieasure  2=;  c.c.  of  —  hydrochloric  acid  from  a  burette 
^  10     -^ 

into  a  300-c.c.  Erlenmeyer  flask  and  place  the  condenser-tip 
beneath  the  surface  of  the  liquid,  adding  a  little  water,  if  nec- 
essary, to  seal  it. 

Rinse  down  the  neck  of  the  digestion-flask  with  100  c.c. 
of  ammonia-free  water,  add  20  c.c.  of  potassium  sulphide 
solution,  and  connect  the  flask  with  the  condenser.  Add  100 
c.c.  of  caustic  potash  through  the  separatory  funnel,  and  dis- 
til off  the  ammonia  by  steam.  When  200  c.c.  have  distilled 
over,  remove  the  collecting-flask,  after  rinsing  off  the  conden- 
ser-tip with  distilled  water,  and  titrate  the  excess  of  acid  with 

N 

—  sodium  hvdroxide,  using  methvl  orange  or  cochmeal  as 

indicator.  A  blank  determination  is  made  with  0.5  gram  of 
cane-sugar  in  order  to  reduce  any  nitrates  present  in  the  re- 
agents which  might  otherwise  escape  detection. 

Notes. — The  temperature  during  the  digestion  must  be 
maintained  at  or  near  the  boiling-point  of  the  acid,  since  at  a 
lower  temperature  the  formation  of  ammonia  is  incomplete. 

The  process  is  considered  by  Dafert  *  to  take  place  in  four 

*  Ztschr.  anal.  Chem.,  24  (i8Sj),  455. 


food:    analytical  methods:    cereals.  185 

steps:  (i)  the  sulphuric  acid  takes  the  elements  of  water  from 
the  organic  matter;  (2)  the  sulphur  dioxide  produced  by  the 
action  of  the  residual  carbon  on  the  sulphuric  acid  exercises 
a  reducing  action  on  the  nitrogenous  bodies;  (3)  the  nitro- 
genous substances  formed  in  this  way  are  converted  to  am- 
monia by  a  process  of  oxidation;  (4)  the  ammonia  formed  is 
fixed  by  the  acid  as  ammonium  sulphate. 

In  some  cases  the  potassium  permanganate  is  necessary 
to  insure  the  complete  conversion  of  the  nitrogenous  bodies, 
into  ammonia,  although  it  is  probable  that  its  use  is  unneces- 
sary in  the  majority  of  analyses. 

The  Kjeldahl  process  in  the  form  outlined  above  is  not 
applicable  to  the  determination  of  nitrogen  in  the  form  of 
nitrates.  In  order  to  render  it  of  more  general  application 
various  modifications  of  the  method  have  been  proposed,  the 
one  generally  used  in  this  country  being  that  suggested  by 
Scovell.*  In  this  method  salicylic  acid  is  used  with  the  sul- 
phuric acid,  being  converted  by  the  nitrate  into  nitro-phenol. 
By  the  use  of  sodium  thiosulphate  or  zinc-dust  this  is  reduced 
to  amido-phenol.  The  amido-phenol  is  transformed  into  am- 
monium sulphate  by  the  heating  with  sulphuric  acid,  the  use 
of  mercury  being  absolutely  necessary  in  this  case  to  secure 
the  complete  transformation. 

The  per  cent,  of  proteids  may  be  found  by  multiplying  the 
per  cent,  of  nitrogen  by  an  appropriate  factor,  the  one  in  gen- 
eral use  being  6.25.  It  is  better  to  use  a  special  factor  for  each 
cereal,  however,  using  the  factor  6.25  only  when  a  special  fac- 
tor is  not  given.  The  factors  for  the  common  cereals  are: 
wheat  5.70,  rye  5.62,  oats  6.31,  maize  6.39,  and  barley  5.82. 

Qualitative  Tests  for  Proteids. — (a)  Biuret  Reaction. 
— To  a  small  quantity  of  the  solution  add  about  i  c.c.  of  di- 

*  U.  S.  Dept.  Agr.,  Bull.  16  i/SS7),  51. 


l86  AIR,    WATER,    AND    FOOD. 

lute  (4  per  cent.)  copper  sulphate  solution  and  then  a  consid- 
erable excess  of  strong  caustic  potash  or  soda.  A  violet  color 
is  produced.  The  test  is  generally  known  as  the  biuret  reac- 
tion because  the  substance  biuret,  CoHgNgOa,  left  on  heating 
urea  to  160°  C,  gives  the  color  under  the  same  conditions.  If 
too  much  of  the  copper  sulphate  solution  be  used,  its  color 
may  conceal  that  of  the  reaction. 

(b)  Xanthoproteic  Reaction. — Strong  nitric  acid  produces  a 
yellow  coloration  of  proteid  matter,  which  is  intensified  on 
warming.  On  treating  the  yellow  mixture  with  ammonia  in 
slight  excess  the  color  is  changed  to  an  orange  or  red  tint. 

(c)  Milloii's  Reaction. — When  proteid  matter  is  boiled 
with  Millon's  reagent  (see  page  211),  a  brick-red  coloration  is 
produced.  A  similar  reaction  is  given  by  gelatin  and  allied 
bodies. 

(d)  Liebcrmaiins  Test. — Heat  the  solid  proteid  with  con- 
centrated hydrochloric  acid.  It  will  dissolve  w'ith  the  gradual 
formation  of  a  blue  coloration,  changing  to  violet  and  brown. 

(e)  Adamkiezvicz  Reaction. — If  glacial  acetic  acid  in  excess 
and  then  strong  sulphuric  acid  are  added  to  a  proteid,  a  vio- 
let color  with  faint  fluorescence  is  produced. 

Note. — Since  many  other  substances  give  a  test  with  cer- 
tain of  the  reagents  employed  to  test  for  proteids,  it  will  be 
obvious  that  a  proteid  can  be  identified  with  certainty  only  by 
employing  a  large  number  of  its  reactions. 

Separation  of  the  Proteids  of  Wheat.  —  As  an  ex- 
ample of  the  principles  involved  in  the  separation  of  vegetable 
proteids  may  be  taken  the  separation  of  the  proteids  of  wdieat. 
The  principal  proteids  found  in  wheat  are  glutenin,  gii^din^ 
cdestin,  and  leucosin.  There  is  also  present  in  wheat  a  certain 
amount  of  nitrogen  in  the  form  of  amides,  and  a  trace 
of  lecithin,  a  nitrogenous  body  allied  to  the  fats.  The  total 
proteid  matter  insoluble  in  cold  water  is  ordinarily  known  as 


food:    analytical  methods:   cereals.  187 

gluten.  It  is  a  mixture  of  the  two  proteids  first  named.  The 
crude  gluten  is  readily  obtained  from  flour  by  kneading  a 
quantity  of  it  in  a  thin  stream  of  cold  water  until  the  starch 
and  soluble  matter  is  removed. 

The  methods  of  separation  depend  in  general  upon  the 
relative  solubility  of  the  proteids  in  dilute  salt  solutions  or  in 
alcohol  of  different  strengths.* 

Edestin  and  Leucosin. — These  may  be  determined  together 
by  first  extracting  a  definite  weight  of  the  finely  ground  ma- 
terial with  a  I  per  cent,  sodium  chloride  solution.  To  an 
aliquot  part  of  the  clear  salt  solution  is  added  sufficient  strong 
alcohol  to  make  the  mixture  75  per  cent,  alcohol.  After 
standing  overnight  the  precipitate  is  filtered  off  and  the  nitro- 
gen in  it  determined.  If  desired,  the  two  proteids  may  be 
separated  by  coagulating  the  leucosin  at  60°  C.  and  precipi- 
tating the  edestin  by  adding  alcohol  to  the  clear  filtrate  as 
before.    The  nitrogen  in  each  precipitate  is  then  determined. 

Amides. — Determined  by  precipitating  all  the  proteids 
from  the  above  salt  solution  by  means  of  phospho-tungstic 
acid.  After  standing  overnight  the  precipitated  proteids  are 
filtered  off  and  the  nitrogen  of  the  amides  in  the  solution  de- 
termined. 

Gliadin. — x\bout  a  gram  of  the  finely  divided  material  is 
extracted  with  hot  alcohol  (sp.  gr.  0.90).  The  filtrate  and 
washings  are  evaporated  to  dryness  in  a  Kjeldahl  flask  and 
the  nitrogen  determined  in  the  residue.  The  per  cent,  of 
nitrogen  found,  less  the  per  cent,  of  amide  nitrogen,  is  the  per 
cent,  of  gliadin  nitrogen. 

Glufemn. — This  is  the  difference  between  the  per  cent,  of 
total  nitrogen  and  the  per  cents,  of  the  edestin,  leucosin, 
gliadin,  and  amide  nitrogen. 

*  G.  L.  Teller:  Ark.  Agr.  Expt.  Sta.,  Bull.  42  (tSg6),  81;  see  also 
Osborne's  papers  in  Am.  Chem.  J.,  I3-IS- 


1 88  AIR,    WATER,    AiND    FUOD. 

The  per  cents,  of  the  various  proteids  may  be  found  by 
multiplying  the  corresponding  nitrogen  by  5.70. 

Carbohydrates. — Total  Carbohydrates. — Generally  deter- 
mined by  subtracting  from  100  the  sum  of  the  per  cents,  of 
the  other  constituents,  viz.,  water,  ash,  fats  and  oils,  and  nitro- 
genous matters.  The  total  carbohydrates  are  made  up  princi- 
pally of  sugars,  starches,  and  crude  fibre,  the  latter  including 
pentosans  and  cellulose. 

Sugars. — The  finely  ground  material,  previously  ex- 
tracted with  petroleum  ether  if  much  oil  is  present,  is  ex- 
tracted for  about  three  hours  with  80  per  cent,  alcohol.  The 
extracted  matter  is  dried  at  a  low  temperature  and  w-eighed. 
Starch. —  The  methods  for  the  determination  of  starch 
vary  with  the  condition  in  which  the  starch  is  found.  In  the 
case  of  nearly  pure  starch  it  may  be  converted  into  dextrose 
by  boiling  with  dilute  acid,  the  dextrose  being  then  deter- 
mined by  Fehling's  solution  in  the  usual  way.  Hot  acids, 
however,  cannot  be  used  to  convert  starch  in  the  natural  state, 
as  it  is  found  in  cereals,  because  other  carbohydrate  bodies 
become  soluble  under  these  conditions.  In  such  cases  the 
starch  is  broug'ht  into  solution  by  treatment  with  diastase  or 
by  heating  with  water  under  pressure. 

For  the  rapid  estimation  of  starch  in  cereals  the  following 
method  has  been  found  useful :  * 

Principle. — Conversion  of  starch  to  dextrin  and  maltose, 
that  is,  solution  of  the  starch  by  diastase  in  malt  extract.  Con- 
version of  dextrin  and  maltose  to  dextrose  by  acid  (hy- 
drolysis). 

Directions. — Place  about  a  gram  of  the  finely  divided  sam- 
ple, the  residue  from  the  extraction  of  sugar,  for  example,  in 
a  flask,  add  50  c.c.  of  water,  3  c.c.  of  malt  extract,  and  boil  for 

*  Hibbard;  /.  Am.  Chem.  Soc,  X'J  {i8gs).  64. 


food:     analytical    METHODS:     CEREALS.  1 89 

one  minute,  with  frequent  shaking.  Cool  the  solution  to 
60°  C,  add  3  c.c.  of  malt  extract,  and  heat  slowly  so  that 
fifteen  minutes  are  required  to  reach  the  boiling-point.  Test 
the  solution  for  starch  by  placing  a  drop  upon  a  porcelain  tile 
and  adding  a  drop  of  solution  of  iodine  in  potassium  iodide. 
Should  a  blue  color  appear,  add  more  mak  extract  and  repeat 
the  heating  until  all  the  starch  has  been  converted.  Cool  the 
solution,  make  it  up  to  lOO  c.c,  and  filter  it  through  fine  linen 
or  cotton  cloth.  To  an  aliquot  part  of  the  filtrate,  25  or  50 
c.c,  in  a  flask,  add  5  c.c  of  hydrochloric  acid  (sp.  gr.  1.15), 
and  enough  water  to  make  the  volume  60  c.c.  Place  a  small 
funnel  in  the  neck  of  the  flask  to  retard  evaporation  and  boil 
the  solution  gently  for  exactly  half  an  hour.  Cool  the  solu- 
tion, add  sodium  hydroxide  until  nearly  neutralized,  and  de- 
termine the  dextrose  by  Fehling's  solution.  A  blank  deter- 
mination should  be  carried  throug'h  under  the  same  conditions 
and  using  the  same  quantities  of  reagents,  in  order  to  make  a 
correction  for  the  sugar  in  the  malt  extract. 

Malt  Extract. — Treat  coarsely  pulverized  dry  malt  for  sev- 
eral hours  with  sufficient  20  per  cent,  alcohol  to  cover  it.  The 
solution  is  then  filtered  and  may  be  kept  for  two  weeks  with- 
out losing  its  diastatic  power. 

If  the  malt  itself  is  not  readily  procurable,  certain  forms  of 
prepared  diastase  are  on  the  market  and  may  be  found  more 
convenient  either  for  analytical  use  or  for  purposes  of  illus- 
tration. When  possible,  however,  it  is  preferable  to  use  the 
freshly  prepared  malt  extract  as  the  prepared  diastase,  made 
at  different  times  and  from  separate  portions  of  malt,  may 
show  great  differences  in  hydrolytic  power. 

Crude  Fibre- — This  may  be  determined  by  the  method 
adopted  by  the  Association  of  Official  Agricultural  Chemists.* 

*  U.  S.  Dept.  Agr..  Div.  of  Chem.,  Bull.  46  [Rev.  Ed.]  (fSgS),  26. 


190  AIR,    WATER,    AND    FOOD. 

% 

EXAMINATION    OF    FERMENTED    LIQUORS. 
WINE. 

Effervescing  wines  should,  before  analysis,  be  vigorously 
shaken  in  a  large  flask,  to  remove  carbon  dioxide. 

Specific  Gravity. — This  is  to  be  taken  by  means  of  the 
Westphal  balance  or  Sprengel  tube  at  15.° 5  C. 

Alcohol  by  Weight. — Principle. — The  alcohol  is  ob- 
tained freed  from  everything  but  water  and  its  amount  deter- 
mined by  ascertaining  the  specific  gravity  of  the  mixture,  and 
taking  the  per  cent,  from  tables. 

Directions. — Weigh  out  about  50  c.c.  of  the  wine  in  a  small 
flask  and  transfer  it  with  100  c.c.  of  water  to  a  500-c.c.  round- 

N        ,. 
bottomed  distilling-flask.   Neutralize  free  acid  with  —sodium 

hydroxide  and  add  0.5  gram  of  tannin,  if  necessary,  to  pre- 
vent frothing.  Distil  off  about  100  c.c.  into  a  150-c.c.  tared 
flask  which  should  be  provided  with  a  cork,  perforated  to  re- 
ceive the  condenser-tip,  and  carrying  a  mercury-valve  to  pre- 
vent loss  of  alcohol.  Weigh  the  distillate,  mix  it  thoroughly, 
and  take  its  specific  gravity  at  I5.°5  C.  with  a  pyknometer. 
The  percentage  of  absolute  alcohol  by  weight  corresponding 
to  the  observed  density  will  be  found  in  Table  X,  page  203. 

Example. — If  A  is  the  percentage  of  absolute  alcohol  in 
the  sample,  a  that  in  the  distillate,  W  and  zv  the  weights  of 

wa 
the  sample  and  distillate  respectively,  then  A  =  j^. 

Notes. — If  the  specific  gravity  of  the  wine  is  known, 
weighing  may  be  avoided  by  carefully  measuring  both  sample 
and  distillate  at  i5.°5  C.  The  corresponding  percentage  of 
alcohol  by  volume  may  be  found  by  appropriate  tables.  (See 
Sadtler's  Industrial  Or-ganic  Chemistry.) 

In  the  case  of  distilled  Hquors  about  30  grams  are  diluted 


lOOD:     ANALYTICAL    METHODS:     FERMENTED    LIQUORS.      I9I 

to  150  C.C.,  TOO  c.c.  distilled,  and  the  per  cent,  of  alcohol  by 
weight  determined  as  above. 

The  object  of  neutralizing  the  wine  with  sodium  hydrox- 
ide is  to  prevent  the  distillation  of  volatile  acids,  principally 
acetic.  A  certain  amount  of  volatile  ethers  may  also  pass 
over  into  the  distillate,  but  in  most  cases  it  is  so  slight  that  its 
influence  may  be  neglected. 

Extract. —  Dry  Wines. — Weigh  out  about  50  c.c.  in  a 
small  flask,  transfer  to  a  platinum  dish  having  a  flat  bottom, 
and  evaporate  on  the  water-bath  to  the  consistency  of  syrup. 
Then  heat  the  residue  in  the  oven  at  100°  C.  for  two  hours 
and  a  half,  cool  in  a  desiccator,  and  weigh. 

Szvcct  Wines. — Weigh  out  10  c.c,  dilute  to  100  c.c,  and 
evaporate  50  c.c.  as  directed  above. 

Notes. — The  extract  is  composed  mainly  of  dextrins, 
sugars,  organic  acids,  nitrogenous  substances,  and  mineral 
matters.  Of  these  the  dextrins  and  sugars  form  the  chief 
part,  the  proteids,  however,  amounting  to  about  ten  per  cent, 
in  the  case  of  beer  made  from  malt. 

Ash. — Ignite  the  extract  at  a  very  low  red  heat. 

Free    Acids :    Total  Acidity   Calculated  as    Tartaric 

N 
Acid. — Titrate  10  c.c.  of  the  wine  with  —  sodium  hydroxide. 

The  end-point  is  reached  when  a  drop  of  the  liquid  placed 

upon  faintly-red  litmus  paper  produces  a  blue  spot  in  the 

middle  of  the  portion  moistened.     Calculate  the  results  as 

N 
tartaric  acid.    One  c.c.  —  sodium  hydroxide  =  0.0075  gram 

of  tartaric  acid. 

Volatile  Acids  Calculated  as  Acetic  Acid- — Measure 
50  c.c.  of  wine  into  a  300-c.c.  flask  provided  with  a  cork  hav- 
ing two  perforations.  One  is  fitted  with  a  tube  C  mm.  in 
diameter  and  blown  out  to  a  bulb  40  mm.  in  diameter  a  short 


192  AIR,    WATER,    AND    FOOD. 

distance  above  the  cork;  this  tube  is  connected  with  a  con- 
denser. The  other  perforation  carries  a  tube  reaching  nearly 
to  the  bottom  of  the  tlask  and  drawn  out  to  a  small  aperture 
at  its  lower  end;  this  is  connected  with  a  500-c.c.  flask  con- 
taining water.  Heat  both  flasks  to  boiling;  then  low^er  the 
flame  under  that  containing  the  wine  and  continue  the  distil- 
lation by  means  of  steam  until  200  c.c.  have  gone  over.     Tit- 

N 
rate  the  distillate  with  —  sodium  hydroxide,  using  phenolph- 

thalein  as  an  indicator.     Calculate  the  results  as  acetic  acid. 

One  c.c.  —  sodium  hvdroxide  =  0.0060  gram  of  acetic  acid. 
10 

Fixed  Acids  Calculated  as  Tartaric  Acid.  —  These 
may  be  found  by  calculating  the  volatile  acids  as  tartaric  and 
subtracting  the  result  from  the  total  tartaric  acid  found  by 
direct  titration. 

Coloring  Matters- — The  various  aniline  colors  are  gen- 
erally used  in  artificially  colored  wines,  the  color  most  com- 
monly occurring  being  fuchsine. 

Caseneuve  Reaction. — Add  0.2  gram  of  precipitated  mer- 
curic oxide  to  10  c.c.  of  the  wine,  shake  for  one  minute  and 
filter.  Pure  wines  give  a  filtrate  which  is  colorless  or  light 
yellow,  while  the  presence  of  a  more  or  less  red  coloration  in- 
dicates the  presence  of  an  aniline  color. 

Detection  of  Fuchsine  and  Orscillc. — To  20  c.c.  of  wine  add 
10  c.c.  of  basic  lead  acetate  solution,  heat  slightly,  and  mix 
by  shaking.  Filter  into  a  test-tube,  add  2  c.c.  of  amyl  alco- 
hol, and  shake.  If  the  amyl  alcohol  be  colored  red,  separate 
it  and  divide  it  into  two  portions.  To  one  add  hydrochloric 
acid,  to  the  other  ammonia.  If  the  color  is  due  to  fuchsine, 
the  amyl  alcohol  will  be  decolorized  in  each  case;  if  due  to 
orseille.  the  ammonia  will  change  the  cole  of  the  amyl  alco- 
hol to  purplish  violet. 


food:   analytical  methods:   fermented  liquors.    193 

Detection  of  Salicylic  Acid. — S pica's  Method. — Acidify 
100  c.c.  of  the  wine  with  sulphuric  acid  and  extract  with  ether. 
Evaporate  the  extract  to  dryness,  warm  the  residue  carefully 
w'ith  one  drop  of  concentrated  nitric  acid  and  add  two  or 
three  drops  of  ammonia.  The  presence  of  salicylic  acid  is  in- 
dicated by  the  formation  of  a  yellow  color,  due  to  ammonium 
picrate,  and  may  be  confirmed  by  immersing  a  thread  of  fat- 
free  wool,  which  will  be  dyed  a  permanent  yellow. 

Girard's  Method. — Extract  a  portion  of  the  acidified  liquor 
with  ether  as  in  the  preceding  method,  evaporate  the  extract 
to  dryness  spontaneously,  and  extract  the  residue  with  petro- 
leum ether.  Evaporate  the  petroleum  ether  extract,  dissolve 
the  residue  in  water  and  add  a  few  drops  of  a  very  dilute  solu- 
tion of  ferric  chloride.  A  violet-red  color  indicates  salicylic 
acid. 

Beer  and  Other  Malt  Liquors- — Before  analysis  the 
sample  must  be  thoroughly  shaken  in  a  large  flask,  in  order 
to  remove  carbon  dioxide. 

Specific  Gravity. — Taken  with  a  pyknometer  or  Sprengel 
tube  at  15. °5  C. 

Alcohol  by  Weight. — Determined  as  in  the  analysis  of  wine, 
using  TOO  c.c.  of  the  sample  and  50  c.c.  of  distilled  water. 

Extract  and  Ash. — Determined  as  in  the  analysis  of  dry 
wines. 

Free  Acids. — Titrated  as  in  the  analysis  of  wine.  Fixed 
acids,  consisting  principally  of  lactic  and  succinic,  are  calcu- 
lated as  lactic  acid.     Volatile  acids  are  calculated  as  acetic 

N 
acid.     One  c.c.  of  —  sodium  hydroxide  =  0.0090  gram  of 

lactic  acid. 

Nitrogen. — Weigh  out  about  20  c.c.  of  the  sample,  transfer 
it  to  a  750-c.c.  round-bottomed  flask,  and  evaporate  almost 
to  dryness  on  the  water-bath.  Determine  the  nitrogen  in  the 
residue  as  on  page  92. 


APPENDIX  A. 

Table  I. 

TENSION    OF   AQUEOUS    VAPOR    IN    MILLIMETERS    OF    MERCURY    FROM 
0°    TO    30°. 9    C,    REDUCED    TO   0°    AND    SEA-LEVEL. 


o°.o. 

o'.i. 

o'.z. 

o°,3. 

o°.4. 

o°.5. 

o°.6. 

o°.7. 

o°.8. 

oo.g. 

0' 

4-57 

4.60 

4.64 

4.67 

4.70 

4-74 

4.77 

4.80 

4.84 

4.87 

I 

4.91 

4.94 

4.98 

5.02 

5.05 

5-09 

5.12 

5.16 

5.20 

5.23 

2 

5-27 

5.31 

5-35 

5-39 

5-42 

5-46 

5.50 

5-54 

5-58 

5.62 

3 

5.66 

5-70 

5-74 

5.78 

5.82 

5.86 

5-90 

5.94 

5.99 

6.03 

4 

6.07 

6. II 

6.15 

6.20 

6.24 

6.28 

6-33 

6.37 

6.42 

6.46 

5 

6.51 

6.55 

6.60 

6.64 

6.69 

6.74 

6.78 

6.83 

6. 88 

6.92 

6 

6.97 

7.02 

7.07 

7-12 

7.17 

7.22 

7.26 

7.31 

7-36 

7.42 

7 

7-47 

7-52 

7-57 

7.62 

7.67 

7.72 

7-78 

7.83 

7.88 

7-94 

8 

7-99 

8.05 

8.10 

8.15 

8.21 

8.27 

8.32 

8.38 

8.43 

8.49 

9 

8.55 

8.61 

8.66 

8.72 

8.78 

8.84 

8.90 

8.96 

9.02 

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10 

9.14 

9.20 

9.26 

9-32 

9-39 

9-45 

9.51 

9.58 

9.64 

9-70 

II 

9-77 

9-83 

9.90 

9.96 

10.03 

10.09 

10.16 

10.23 

10.30 

10.36 

12 

10.43 

10.50 

10.57 

10.64 

10.71 

10.78 

10.85 

10.92 

10.99 

11.06 

13 

II. 14 

II. 21 

11.28 

11.36 

11-43 

11.50 

11.58 

11.66 

11-73 

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14 

11.88 

11.96 

12.04 

12.12 

12. ig 

12.27 

12.35 

12.43 

12.51 

12.59 

15 

12.67 

12.76 

12.84 

12.92 

13.00 

13.09 

13.17 

13.25 

13-34 

13.42 

16 

13-51 

13.60 

13.68 

13-77 

13.86 

13-95 

14.04 

14.12 

14.21 

14.30 

17 

14.40 

14.49 

14.58 

14.67 

14.76 

14.86 

14-95 

15.04 

15.14 

15-23 

18 

15-33 

15-43 

15-52 

15.62 

15-72 

15-82 

15-92 

16.02 

16.12 

16.22 

19 

16.32 

16.42 

16.52 

16.63 

16.73 

16.83 

16.94 

17.04 

17.15 

17.26 

20 

17-36 

17-47 

17-58 

17.69 

17.80 

17-91 

18.02 

18.13 

18.24 

18.35 

21 

18.47 

18.58 

18.69 

18.81 

18.92 

19.04 

19.16 

19.27 

19.39 

19-51 

22 

19.63 

19-75 

19.87 

19.99 

20.  II 

20.24 

20.36 

20. 48 

20.61 

20.73 

23 

20.86 

20.98 

21. II 

21 .24 

21-37 

21.50 

21.63 

21.76 

21.89 

22.02 

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22.15 

22.29 

22.42 

22.55 

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22.83 

22.96 

23. 10 

23-24 

23.38 

25 

23.52 

23.66 

23.80 

23-94 

24.  oS 

24.23 

24.37 

24.52 

24.66 

24.81 

26 

24.96 

25.10 

25.25 

25.40 

25-55 

25.70 

25.86 

26.01 

26.16 

26.32 

27 

26.47 

26.63 

26.78 

26.94 

27.10 

27.26 

27.42 

27.58 

27-74 

27.90 

28 

28.07 

28.23 

28.39 

28.56 

28.  73 

28.89 

29.06 

29.23 

29.40 

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29.74 

29.92 

30.09 

30.26 

30.44 

30.62 

30.79 

30.97 

31-15 

31-33 

30 

31-51 

31.69 

31.87 

32.06 

32.24 

32-43 

32.61 

32.80 

32.99 

33-18 

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APPENDIX  A. 

Table  VII. 


TABLE     OF     HARDNESS,      SHOWING      THE      PARTS      OF     CALCIUM    CAR- 
BONATE   (CaCO,)    IN    1,000,000    FOR    EACH    TENTH    OF   A    CUBIC 
CENTIMETER    OF    SOAP    SOLUTION    USED. 


0.0 

0.1 

0.2 

0.3 

0.4 

o-S 

0.6 

0.7 

0.8 

0.9 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

0.0 

0.0 

1.6 

3-2 

1 .0 

4.8 

6.3 

7.9 

9-5 

II. I 

12.7 

14-3 

15.6 

16.9 

18.2 

2.0 

19-5 

20.8 

22.1 

23-4 

24.7 

26.0 

27-3 

28.6 

29-9 

31.2 

3-0 

32-5 

33.8 

35.1 

36.4 

37.7 

390 

40.3 

41.6 

42.9 

44-3 

4.0 

45-7 

47.1 

48. 6 

50.0 

51-4 

52.9 

54.3 

55-7 

57.1 

58.6 

5.0 

60.0 

61.4 

62.9 

64-3 

65.7 

67.1 

68.6 

70.0 

71.4 

72.9 

6.0 

74-3 

75-7 

77-1 

78.6 

80.0 

81.4 

82.9 

84-3 

85-7 

87.1 

7.0 

88.6 

90.0 

91.4 

92.9 

94-3 

95.7 

97.1 

98.6 

100. 0 

101.5 

8.0 

103.0 

104.5 

106.0 

107.5 

109.0 

II0.5 

112. 0 

II3-5 

I15-0 

116. 5 

9.0 

118. 0 

II9-5 

121. 1 

122.6 

124. 1 

125.6 

127. 1 

128.6 

130. 1 

131. 6 

10. 0 

I33-I 

134.6 

136. 1 

137-6 

139- 1 

140.6 

142. 1 

143-7 

145.2 

146.8 

11. 0 

148.4 

150.0 

151-6 

153-2 

154.8 

156.3 

157.9 

159-5 

161. 1 

162.7 

12.0 

164.3 

165.9 

167.5 

169.0 

170.6 

172.2 

173-8 

175.4 

177.0 

178.6 

13.0 

180.2 

181. 7 

183.3 

184.9 

186.5 

188. 1 

189.7 

191-3 

192.9 

194.4 

14.0 

196.0 

197.6 

199.2 

200.8 

202.4 

204.0 

205.6 

207.1 

208.7 

210.3 

I5-0 

211.9 

213-5 

215. 1 

216. 8 

218.5 

220.2 

221.8 

223.5 

225.2 

226.9 

Table  VIII. 

SHOWING    THE    NUMBER    OF     CUBIC     CENTIMETERS     OF    OXYGEN     DIS- 
SOLVED   IN     1000    CUBIC    CENTIMETERS    OF    WATER    WHEN 
SATURATED    AT    DIFFERENT    TEMPERATURES,    AS   CAL- 
CULATED   BY    WINKLER.* 


Deg.  Cent. 

Cu.  Cm. 

Deg.  Cent. 

Cu.  Cm. 

Deg.  Cent. 

Cu.  Cm. 

0 

10.187 

II 

7.692 

21 

6.233 

I 

9.910 

12 

7.518 

22 

6. 114 

2 

9.643 

13 

7.352 

23 

5-999 

3 

9-387 

14 

7.192 

24 

5.886 

4 

9.142 

15 

7.03S 

25 

5.776 

5 

8. 907 

16 

6.891 

26 

5.669 

6 

8.682 

17 

6.750 

27 

5-564 

7 

8.467 

18 

6.614 

28 

5.460 

8 

8. 260 

19 

6.482 

29 

5.357 

9 

8.063 

20 

6.356 

30 

5-255 

10 

7-S73 

*  Berichte,  22  {i88g),  1772. 


APPENDIX   A. 


20I 


Table  IX. 


FOR   CORRECTING    THE     SPECIFIC    GRAVITY    OF    MILK   ACCORDING     TO 
TEMPERATURE.       ADAPTED    FROM    THE    TABLE    OF    VIETH. 

(Temperature  in  Degrees  Centigrade.) 


Specific 
Gravity. 

10° 

11° 

12° 

13° 

14° 

15° 

16° 

17° 

18° 

19°       20° 

1.025 

24.1 

24-3 

24-5 

24.6 

24-7 

24.9 

25-1 

25.3 

25-4 

1 
25.6;  25.9 

26 

25  I 

25.2 

25-4 

25 

5 

25.7 

25.9 

26. 1 

26.3 

26.5 

26. 7j  27.0 

27 

26.1 

26.2 

26.4 

26 

5 

26.7 

26.9 

27.1 

27.4 

27-5 

27.7)  28.0 

28 

27.0 

27.2 

27.4 

27 

5 

27.7 

27.9 

28.1 

28.4 

28.5 

28.71  29.0 

29 

28.0 

28.2 

28.4 

28 

5 

28.7 

28.9 

29. 1 

29.4 

29-5 

29.8    30.1 

30 

29.0 

29.1 

29-3 

29 

5 

29.7 

29.9 

30.1 

30.4 

30-5 

30.8 

311 

31 

29.9 

30.1 

30.3 

30 

4 

30.6 

30.9 

31.2 

31-4 

3^-5 

31-8 

32.2 

32 

30.9 

31. 1 

31-3 

31 

4 

31.6 

31-9 

32.2 

32-4 

32.6 

32.9 

33-2 

33 

31-8 

32.0 

32.3 

32 

4 

32.6 

32-9 

33-2 

33-4 

33-6 

33-9 

34-2 

34 

32.7 

33.0 

33-2 

33 

4 

33-6 

33-9 

34-2 

34-4 

34-6 

34-9 

35-2 

35 

33-6 

33-9 

34-1 

34 

4 

34-6 

34-9 

35-2 

35-4 

35-6 

35-9 

36.2 

Directions. — Find  the  observed  gravity  in  the  left-hand  column.  Then 
in  the  same  line,  and  under  the  observed  temperature,  will  be  found  the 
corrected  reading. 


202 


APPENDIX    A. 


Table    X. 


PERCENTAGE  OF  ALCOHOL  BY  WEIGHT    FROM    THE    SPECIFIC    GRAVITY 

AT  i5°.5  c.     (hehner.) 


Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Sp.  Gr. 

Alcohol 

Sp.  Gr. 

Alcohol 

Sp.  Gr. 

Alcohol 

Sp.  Gr. 

Alcohol 

15°. 5  C. 

by 

iS°-5  C. 

by 

i5».sC. 

by 

'S'-S  C. 

^by 

Weight. 

Weight. 

Weight 

Weight. 

I. 0000 

0.00 

7 

2.44 

4 

5.00 

I 

7.87 

0.9999 

8 

7 
6 

0.05 

0.  II 
0.  16 
0.21 

6 
5 
4 
3 
2 
I 

2.50 
2.56 
2.61 
2.67 
2.72 
2.78 
2. S3 

3 
2 

I 
0 

5.06 
5.12 
5.19 

5-25 

0 

0.9869 

8 
7 

7-93 

8.00 

8.07 
8.14 

5 

0.26 

0.9909 

5-31 

6 

8. 21 

4 

0.32 

0 

8 

5-37 

5 

8.29 

3 

0.37 

7 

5.44 

4 

8.36 

2 

0.42 

0.9949 

2.89 

6 

5.50 

3 

8.43 

I 

0.47 

8 

2.94 

5 

5.56 

2 

8.50 

0 

0.53 

7 

3.00 

4 

5-62 

I 

8.57 

0.9989 

8 

7 
6 

0.58 

0.63 
0.63 

0.74 

6 

5 
4 
3 

3.06 
3.  12 

3.18 

3  24 

3 
2 

I 
0 

5-69 

5.75 
5. Si 
5-87 

0 

0.9859 

8 

7 

8.64 

8.71 

8.79 
8.86 

5 
4 
3 

0.79 
0.84 
0.89 

2 

I 
0 

3-29 
3-35 
3-41 

0.9899 

8 
7 

5-94 

6.00 
6.07 

6 
5 
4 

8.93 
9.00 
9.07 

2 

0.95 

0.9939 

3-47 

6 

6. 14 

3 

9.14 

I 

1. 00 

8 

3-53 

5 

6.21 

2 

9.21 

0 

1.06 

7 

3-59 

4 

6.28 

I 

9.29 

0.9979 

8 

7 

1. 12 

1. 19 

1.25 

6 
5 
4 
3 

3-65 
3-71 
3-76 
3.82 

3 
2 
I 

0 

6.36 

6-43 
6.  50 

6.57 

0 

0.9849 

8 

9-36 

9-43 

9- 50 

6 

I -31 

2 
I 

0 

3.88 

3-94 
4.00 

7 

9-57 

5 
4 
3 

1-37 
1.44 
1.50 

0.9889 

8 
7 

6.64 

6.71 
6. 78 

6 
5 
4 

9.64 
9.71 
9-79 

2 

1.56 

0.9929 

4.06 

6 

6.86 

3 

9.86 

I 

1.62 

8 

4.12 

5 

6.93 

2 

9-93 

0 

1.69 

7 

4.19 

4 

7.00 

I 

10.00 

0.9969 

1-75 

6 
5 
4 

4-25 
4-31 
4-37 

3 
2 

I 

7.07 

7-13 
7.20 

0 

10.08 

8 
7 

1. 81 
1.87 

0.9839 

8 

10.15 

10.  23 

6 

1.94 

3 

4.44 

0 

7.27 

7 

10.31 

5 

2.00 

2 

T 

4.50 
4.56 
4.62 

0.9879 

7-33 

6 

10. 38 

4 

2.06 

0 

8 

7.40 

5 

10.46 

3 

2. II 

7 

7-47 

4 

10.54 

2 

2.17 

0.9919 

4.69 

6 

7-53 

3 

10.62 

I 

2.22 

8 

4-75 

5 

7.60 

2 

10.69 

0 

2.28 

7 

4.81 

4 

7.67 

I 

10.77 

0.9959 

8 

2.33 

2.39 

1 

6 

5 

4.87 
4.94 

3 
2 

7.73 
7.80 

0 
0.9829 

10.85 
10.92 

APPENDIX    A. 


20' 


Table    X. — Continued. 
PERCENTAGE    OF    ALCOHOL    BY    WEIGHT. 


Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Sp.  Gr. 

Alcohol 

Sp.  Gr. 

Alcohol 

Sp.  Gr. 

Alcohol 

Sp.  Gr. 

Alcohol 

15°. 5  C. 

by 

is-.s  c. 

by 

i5°-5  C. 

by 

is°.s  C. 

by 

Weight. 

Weight. 

Weight. 

Weight. 

0.9829 

10.92 

4 

14-45 

0.9739 

18.15 

4 

21.77 

8 

11.00 

3 

14-55 

8 

18.23 

3 

21.85 

7 

ii.oS 

2 

14.64 

7 

18.31 

2 

21.92 

6 

II. 15 

I 

14-73 

6 

18.38 

1 

22.00 

5 

11.23 

0 

14.82 

5 

18.46 

0 

22.08 

4 
3 
2 

II. 31 
11.38 
11.46 

0.9779 

8 
7 

14.90 

15.00 
15.08 

4 
3 
2 

18.54 
1S.62 
1S.69 

0.9689 

8 
7 

22.15 

22.23 
22.31 

I 
0 

11-54 
11.62 

6 

,    5 

15.17 
15.25 

I 
0 

18.77 

18.85 

6 

5 

22.38 
22.46 

0.9819 

11.69 

4 

15-33 

0.9729 

18.92 

4 

22.54 

8 

11.77 

3 

15.42 

8 

19.00 

3 

22.62 

7 

11.85 

2 

15-50 

7 

19.08 

2 

22.69 

6 

11.92 

I 

15-58 

6 

19.17 

1 

22.77 

5 

12.00 

0 

15.67 

5 

19-25 

0 

22. 85 

4 
3 

12.08 
12. 15 

0.9769 

8 

IS-7S 

15-83 

4 
3 

19-33 
19.42 

0.9679 

8 

22.92 

23.00 

2 

I 

12.23 
12.31 

7 
6 

15-92 
16.00 

2 
I 

19.50 
19-58 

7 
6 

23.08 
23.15 

0 

12.38 

5 

16.08 

0 

19-67 

5 

23 .23 

0.9809 

12.46 

4 

16.15 

0.9719 

19-75 

4 

23-31 

8 

12.54 

3 

16.23 

8 

19.83 

3 

23-38 

7 

12.62 

2 

T6.31 

7 

19-92 

2 

23.46 

6 

12. 6g 

I 

16.38 

6 

20.00 

I 

23-54 

5 

12.77 

0 

16.46 

5 

20.08 

0 

23.62 

4 
3 

12.85 
12.92 

0-9759 

8 

16.54 

16.62 

4 
3 

20.17 
20.25 

0.9669 

8 

23.69 

23-77 

2 

I 

13.00 
13-08 

7 
6 

16.69 
16.77 

2 

I 

20.33 
20.42 

7 
6 

23-85 
23.92 

0 

13-15 

5 

16.85 

0 

20.50 

5 

24.00 

0.9799 

13-23 

4 

16.92 

0.9709 

20.58 

4 

24.  oS 

8 

13-31 

3 

17.00 

8 

20.67 

3 

24-15 

7 

13-3S 

2 

17.08 

7 

20.75 

2 

24.23 

6 

13.46 

I 

17-17 

6 

20.  S3 

I 

24.31 

5 

13-54 

0 

17-25 

5 

20.92 

0 

24.38 

4 
3 

13.62 
13.69 

0.9749 

8 

17-33 

17.42 

4 
3 

21.00 
21.08 

09659 

8 

24.46 

24-54 

2 

I 
0 

13-77 
13-85 
13.92 

7 
6 

5 

17-50 
17-58 
17-67 

2 

I 
0 

21.15 
21.23 
21 .31 

7 
6 

5 

24.62 
24.69 
24-77 

0.9789 

14.00 

4 

17-75 

0.9699 

21.38 

4 

24.85 

8 

14.09 

3 

17.83 

8 

21.46 

3 

24.92 

7 

14.18 

2 

17-92 

7 

21.54 

2 

25.00 

6 

14.27 

I 

18.00 

6 

21 .62 

5 

14-36 

0 

18.08 

5 

21.69 

APPENDIX  B. 

REAGENTS. 
AIR    ANALYSIS. 

Barium  Hydroxide. — A  solution  containing-  about  4  grams 
of  BaO  to  the  liter,     (i  c.c.  =  i  mg.  COo,  approximately.) 

Sulphuric  Acid. — Dilute  46.51  c.c.  of  normal  sulphuric 
acid  to  one  liter,  (i  c.c.  =  i  mg.  COo.)  To  standardize  the 
solution  measure  25  c.c.  into  a  weighed  platinum  dish,  add 
one  drop  of  phenolphthalein  solution  and  titrate  with  the 
barium  hydroxide  to  a  faint  pink.  Evaporate  to  dryness  on 
the  water-bath,  ignite,  and  weigh  as  barium  sulphate. 

Standard  Limc-zcatcr.  (For  Popular  Tests.) — Shake  one 
part  of  freshly  slaked  lime  with  20  parts  of  distilled  water  for 
twenty  minutes  and  let  the  solution  stand  overnight  or  until 
perfectly  clear.  This  solution  should  be  very  nearly  equiva- 
lent to  the  above  standard  sulphuric  acid.  Now  to  a  liter  of 
■distilled  water  add  5  c.c.  of  a  solution  of  0.7  gram  of 
phenolphthalein  in  100  c.c.  of  50  per  cent,  alcohol  and  add 
lime-water  drop  by  drop  until  a  slight  permanent  pink  color 
is  produced.  Add  12.6  c.c.  of  the  above  calcium  hydroxide 
solution.  The  resulting  solution  is  the  standard  lime-water 
used  for  the  tests. 

WATER    ANALYSIS. 

For  Ammonia. —  Water  Free  from  Ammonia. — The  am- 
monia-free water  used  in  this  laboratorv^  is  made  by  redis- 
tilling distilled  water  from  a  solution  of  alkaline  permangan- 

204 


APPENDIX    B. 


205 


ate  in  a  steam-heated  copper  still.  The  apparatus  used  is 
shown  in  Fig.  10.  Only  the  middle  portion  of  the  distillate 
is  collected.  Oftentimes  the  distillate  from  a  good  spring- 
water  may  be  used. 

A^cssler's  Reagent. — Dissolve  61.750  grams  KI  in  250  c.c. 
distilled  water  and  add  a  cold  solution  of  HgCU  which  has 
been  saturated  by  boiling  an  excess  of  the  salt  and  allowing 
it  to  crystallize  out.  Add  the  HgCL  cautiously  until  a  slight 
permanent  red  precipitate  (Hgia)   appears.     Dissolve   this 


Fig.  10. — Still  for  Ammonia-free  Water. 


slight  precipitate  by  adding  0.750  gram  powdered  KI.  Then 
add  1.50  grams  of  KOH  dissolved  in  250  c.c.  of  water.  Make 
up  to  the  liter  and  allow  it  to  stand  overnight  to  settle.  This 
solution  should  give  the  required  color  with  ammonia  within 
five  minutes,  and  should  not  precipitate  within  two  hours. 

Alkaline  Permanganate. — Dissolve  233  grams  of  the  best 
stick  potash  in  350  c.c.  of  distilled  water.     Filter  this  strong 


206  APPENDIX    B. 

solution,  if  necessary,  through  a  layer  of  glass  wool  on  a  por- 
celain lilter-plate.  Dilute  with  700  to  750  c.c.  of  distilled 
water  to  a  sp.  gr.  of  1.125,  add  8  grams  of  potassium  per- 
manganate crystals,  and  boil  down  to  one  liter  to  free  the 
solution  from  nitrogen.  Each  new  lot  of  reagent  must  be 
tested  before  being  used,  but  when  the  chemicals  used  are  all 
good  there  should  be  no  correction  needed  for  ammonia  in 
the  solution. 

Standard  Ammonia  Solution. — Dissolve  3.8215  grams 
chemically  pure  NH4CI  in  a  liter  of  water  free  from  ammo- 
nia. This  is  the  strong  solution  from  which  the  standard 
solution  is  made  by  diluting  10  c.c.  to  a  liter  with  water  free 
from  ammonia.  One  c.c.  of  the  standard  solution  =  O.ODOOI 
gram  nitrogen.  This  solution,  like  the  nitrite  standard  and 
other  dilute  solutions,  must  be  preserved  in  sterilized  bottles 
protected  from  dust  and  organic  matter. 

For  Nitrites. — Standard  Nitrite  Solution. — The  pure  sil- 
ver nitrite  used  in  making  this  solution  is  prepared  by  the 
double  decomposition  of  silver  nitrate  and  potassium  nitrite, 
and  repeated  crystallizations  from  water  of  the  rather  diffi- 
cultly soluble  silver  nitrite,  i.i  grams  of  this  silver  nitrite 
are  dissolved  in  nitrite-free  water,  the  silver  completely  pre- 
cipitated by  the  addition  of  the  standard  salt  solution  used  in 
the  determination  of  chlorine,  and  the  solution  made  up  to 
I  liter.  100  c.c.  of  this  strong  solution  are  diluted  to  i  liter, 
and  10  c.c.  of  this  last  solution  again  diluted  to  i  liter.  The 
final  solution  is  the  one  used  in  preparing  standards,  i  c.c. 
=  0.0000001  gram  nitrogen. 

Hydrochloric  Acid. — i  part  of  pure  HCl  (sp.  gr.  1.20)  is 
diluted  wdth  three  parts  water. 

Sulphanilic  Acid. — Dissolve  8  grams  (Kahlbaum's)  in  i 
liter  of  water.    This  is  a  saturated  solution. 

Naphtylamine   Hydrochlorate. — Dissolve    8    grams    of   a- 


APPENDIX   B.  207 

naphtylamine  in  992  c.c.  of  water  and  add  8  c.c.  of  strong 
HCl.     (Keep  in  the  dark.) 

Ilosz'ay's  Modification. — (a)  Siilphanilic  Acid:  Dissolve  0.5 
gram  of  siilphanilic  acid  in  150  c.c.  of  acetic  acid,  sp.  gr.  1.04. 

{b)  Naphtylamine  Acetate:  Boil  o.i  gram  of  a-naphtyla- 
mine  in  20  c.c.  of  water,  filter  through  a  plug  ot  washed  ab- 
sorbent cotton,  and  add  180  c.c.  of  acetic  acid,  sp.  gr.  1.04. 

For  Nitrates. — Standard  Nitrate  Solution. — Dissolve 
0.720  gram  of  pure  recrystalhzed  KNO3  in  i  liter  of  water. 
Evaporate  10  c.c.  of  this  strong  solution  cautiously  on  the 
water-bath,  moisten  quickly  and  thoroughly  with  2  c.c.  of 
phenol-disulphonic  acid,  and  dilute  to  i  liter  for  the  stand- 
ard solution.     I  c.c.  =  0.000001  gram  nitrogen. 

Phenol-disulphonic  Acid. — Heat  together  3  grams  synthetic 
phenol  with  37  grams  pure,  concentrated  H2SO4  in  a  boil- 
ing-water bath  for  six  hours. 

For  Kjeldahl  Process- — Sidphuric  Acid. — Sp.  gr.  1.84. 
This  should  be  free  from  nitrogen.  May  be  obtained  from 
Baker  and  Adamson,-Easton,  Pa. 

Potassium  Hydroxide. — Dissolve  350  grams  of  the  best 
stick  potash  in  1.25  liters  of  water  and  boil  down  to  some- 
thing less  than  a  liter  with  3  grams  of  permanganate  crystals. 
When  cold,  dilute  to  a  liter  with  water  free  from  ammonia. 

For  Chlorine. — Salt  Solution. — Dissolve  16.48  grams  of 
fused  NaCl  in  a  liter  of  distilled  water.  For  the  standard  so- 
lution dilute  100  c.c.  of  this  strong  solution  to  i  liter,  i  c.c. 
=  0.00 1  gram  chlorine. 

Potassium  Chromate. — Dissolve  50  grams  neutral  K2Cr04 
in  a  little  distilled  water.  Add  enough  AgNO^^  to  produce  a 
slight  red  precipitate.  Filter  and  make  the  filtrate  up  to  a 
liter  with  water  free  from  chlorine. 

Milk  of  Alumina  for  Decoloriaation. — Dissolve  125  grams 
of  potash  or  ammonia  alum  in  a  liter  of  distilled  water.   Pre- 


208  APPENDIX    B. 

cipitate  the  Al(OH)3  by  the  cautious  addition  of  NH4OH. 
Wash  the  precipitate  in  a  lars^e  jar  by  decantation  until  free 
from  chlorine,  nitrites,  and  annnonia. 

For  Hardness. — Standard  Calcium  Chloride  Solution. — 
Dissolve  0.200  gram  of  pure  Iceland  spar  in  dilute  HCl,  tak- 
ing care  to  avoid  loss  by  spattering,  and  evaporate  to  dryness 
several  times,  to  remove  the  excess  of  acid.  Dissolve  the 
calcium  chloride  thus  formed  in  i  liter  of  water. 

Standard  Soap  Solution: — Dissolve  100  grams  of  the  best 
white,  dry  castile  soap  In  a  liter  of  80  per  cent,  alcohol.  Of 
this  strong  solution  dissolve  75-100  c.c.  in  a  liter  of  70  per 
cent,  alcohol.  This  solution  must  have  70  per  cent,  alcohol 
added  to  it  until  14.25  c.c.  of  it  give  the  required  lather  with 
50  c.c.  of  the  above  CaCU  solution. 

Erythrosinc  Indicator. — Dissolve  o.  i  gram  of  erythrosine 
in  I  liter  of  water. 

For  Iron- — Standard  Iron  Solution. — Dissolve  0.86  gram 
of  ferric  ammonium  alum,  (NH4)2S04.Fe2(S04)3.24H20,  or 
a  corresponding  amount  of  the  potassium  salt  in  500  c.c.  of 
water,  add  5  c.c.  HNO3  (i-2o),  and  dilute  to  i  liter,  i  c.c.  = 
0.000 1  gram  Fe. 

Potassium  Sulphocyanidc. — 5  grams  per  liter. 

Hydrochloric  Acid. — i  part  HCl  (sp.  gr.  1.20)  to  i  part  of 
water. 

Potassium  Permanganate. — 5  grams  KMn04  in  i  liter  of 
water. 

For  Dissolved  Oxygen. — 

(a)  48  grams  of  MnS04.4HoO  in  100  c.c.  of  water. 

(&)  360  grams  of  NaOH  and  100  grams  of  KI  in  i  liter 
of  water. 

(c)  HCl,  sp.  gr.  1.20. 

Sodium  Thiosidphate  Solution. — Dissolve  25  grams  of  pure 
recrystallized  sodium  thiosulphate  in  i  liter  of  water.    Dilute 


APPENDIX    B.  209 

100  c.c.  to  I  liter  and  standardize  against  a  known  KaCraOT 
solution. 

For  Lead. — Standard  Lead  Solution. — To  a  strong  solu- 
tion of  lead  acetate  add  a  slight  excess  of  H2SO4,  filter  off 
and  wash  the  precipitate.  Dissolve  it  in  ammonium  acetate 
solution,  made  by  neutralizing  glacial  acetic  acid  with  strong 
ammonia.  Make  up  to  a  known  volume  and  determine  the  lead 
in  an  aliquot  part  by  precipitating  with  KoCroO^  and  weigh- 
ing the  lead  chromate.  Dilute  an  aliquot  part  to  make  a  con- 
venient standard,  say  about  i  c.c.  =  o.ooi  gram  of  Pb, 

FOOD    ANALYSIS. 

For  Milk  Analysis- — Gasolene  (Petroleum  Ether). — ^Gaso- 
lene, sp.  gr.  86°  B.,  which  leaves  no  residue  upon  evaporation 
at  60°  F. 

Fehling's  Solution. — (a).  Dissolve  69.28  grams  of  C.P. 
crystallized  copper  sulphate,  carefully  dried  between  blotting- 
paper,  in  I  liter  of  water  and  add  i  c.c.  of  strong  sulphuric 
acid. 

(b)  Dissolve  346  grams  of  sodium  potassium  tartrate  and 
80  grams  of  sodium  hydroxide  in  i  liter  of  water. 

Potassium  Ferrocyanide. — Dissolve  i  part  in  50  parts  of 
water. 

Aeid  Mercuric  Nitrate. — Dissolve  mercury  in  double  its 
weight  of  nitric  acid  (sp.  gr.  1.42)  and  dilute  the  solution  with 
five  times  its  volume  of  water. 

Fuchsin  Sulphurous  Acid. — Dissolve  i  part  of  a  rosaniline 
salt  in  1000  parts  of  water  and  add  enough  strong  sulphurous 
acid  to  destroy  the  red  color  on  standing. 

For  Butter  Analysis. — Pumice. — Bits  of  ignited  pumice, 
about  the  size  of  a  pea,  dropped  while  hot  into  water  and 
bottled  for  use. 


2IO  APPENDIX    B. 

Alcohol  (for  Reichert-Meissl  method). — 95  per  cent,  alco- 
hol redistilled  from  potassium  hydroxide. 

Potassium  Hydroxide  (for  Reichert-Meissl  method). — One 
part  good  quality  caustic  potash  dissolved  in  one  part  of 
water. 

Glyccrinc-soda  (for  Leffman-Beam  method). — Add  20  c.c. 
of  a  50  per  cent,  solution  of  sodium  hydroxide  to  180  c.c.  of 
pure  concentrated  glycerine.  The  soda  must  be  as  nearly 
free  from  carbonate  as  possible. 

lodo-mercuric  Solution. — Dissolve  25  grams  of  iodine  in 
500  c.c.  of  95  per  cent,  alcohol;  dissolve  also  30  grams  of 
mercuric  chloride  in  500  c.c.  of  95  per  cent,  alcohol.  Mix  the 
two  solutions  and  filter  after  standing  24  hours. 

Potassium  Iodide. — Dissolve  150  grams  of  potassium 
iodide  in  i  liter  of  water. 

For  Cereals. — Anhydrous  Ether. — Wash  ordinary  ether 
several  times  with  distilled  water  and  add  solid  caustic  potash 
until  most  of  the  water  has  been  removed.  Then  add  small 
pieces  of  clean  metallic  sodium  until  there  is  no  further  evolu- 
tion of  hydrogen  gas.  The  ether  thus  prepared  should  be 
kept  over  metallic  sodium  and  the  bottle  should  be  only 
lightly  stoppered,  in  order  to  allow  of  the  escape  of  any  accu- 
mulated gas. 

Potassium  Sulphide. — Dissolve  40  grams  of  the  crystal- 
lized salt  in  I  liter  of  water  and  filter. 

Potassium  Hydroxide  (for  Kjeldahl  process). — Sp.  gr.  = 
1.25.  Dilute  a  liter  of  this  solution  to  about  1.25  liters  and 
boil  down  to  something  less  than  a  liter  with  3  grams  of  po- 
tassium permanganate.    When  cold  dilute  to  a  liter. 

Phospho-tungsfic  Acid. — Dissolve  50  grams  of  the  crystal- 
lized acid  in  dilute  hydrochloric  acid,  containing  25  grams  of 
HCl  to  the  liter. 

Basic  Lead  Acetate. — Boil  for  half  an  hour  440  grams  of 


APPENDIX    B.  211 

lead  acetate  and  264  grams  of  litharge  in  1500  c.c.  of  water. 
Cool  and  dilute  to  2  liters.  Allow  to  settle  and  siphon  off  the 
clear  liquor.  (Sp.  gr.  about  1.27,  containing  about  35  per 
cent,  of  the  basic  salt.) 

Millon's  Reagent. — Dissolve  mercury  in  twice  its  weight  of 
nitric  acid  (sp.  gr.  1.42)  and  dilute  the  sohition  obtained  with 
three  times  its  volume  of  water. 


BIBLIOGRAPHY. 


The  following  list  comprises  some  of  the  more  important 
works  bearing  on  the  subjects  treated  in  the  preceding  pages. 
A  bibliography  of  the  chemistry  of  foods  complete  to  1882 
may  be  found  in  the  Second  Annual  Report  of  the  New- 
York  State  Board  of  Health,  and  more  or  less  complete 
bibliographies  are  to  be  found  in  Sadtler's  "  Industrial  Or- 
ganic Chemistry  "  and  Blyth's  "  Composition  and  Analysis 
of  Foods." 

AIR. 

Air  and  Rain.     R.  Angus  Smith.     Longmans,  Green  &  Co.     London.     1872. 

Air  and  Its  Relations  to  Life.  Walter  N.  Hartley.  D.  Appleton  &  Co. 
New  York.    T8'75. 

Report  on  the  Air  of  Glasgow.  E.  M.  Dixon.  Robert  Anderson.  Glas- 
gow.    1877. 

Recherches  sur  I'Air  Confine.     A.  Braud.     Bailliere  et  Fils.     Paris.      1880. 

Air  Analysis.  J.  A.  Wanklyn  and  W.  J.  Cooper.  Kegan  Paul,  Trench, 
Trlibner  &  Co.     London.     1890. 

Les  Poisons  de  I'Air.     N.  Grehaut.     Bailliere  et  Fils.     Paris.     1890. 

Treatise  on  Hygiene  and  Public  Health.  Vol.  I.  Thomas  Stevenson  and 
S.  F.  Murphy.      Blakiston,  Son  &  Co.      Phila.      1892. 

Air  and  Water.     Vivian  B.  Lewes.     Methuen  &  Co.     London.     1892. 

Methods  for  the  Determination  of  Organic  Matter  in  Air.  D.  H.  Bergey. 
Smithsonian  Institution.     Washington,  D.  C.      1896. 

The  Detection  and  Measurement  of  Inflammable  Gas  and  Vapor  in  the 
Air.     Frank  Clowes.  ^  Crosby,  Lockwood  &  Son.     London.     1896. 

VENTILATION. 

Heating  and  Ventilation  of  the  New  Building,  Mass.  Inst.  Tech.  S.  II. 
Woodbridgc.     Tech.  Quart.,  2,  7C.      1888. 

213 


214  BIBLIOGRAPHY. 

Heating  and  Ventilation.     J.  S.  Billings.     Sanitary  Engineer.     New  York. 

1893. 
Heating  and  Ventilating  Buildings.     Rolla  C.  Carpenter.     John  Wiley  & 

Sons.     New  York.      1S95. 

WATER. 

Report  of  the  Royal  Commission  on  Water  Supply.  Great  Britain  Par- 
liamentary Documents.     London.      i86g-'7o. 

Sixth  Report  of  Rivers  Pollution  Commission,  Great  Britain.  London. 
1S76. 

Potable  Waters.     C.  Ekin.     1880. 

Water  Supply  (Considered  mainly  from  a  Chemical  and  Sanitary  Stand- 
point).    W.  R.  Nichols.     John  Wiley  &  Sons.     New  York.     1883. 

Water  Analysis  for  Sanitary  Purposes.  E.  Frankland.  John  Van  Voorst. 
London.     1890. 

The  Organic  Analysis  of  Potable  Waters.     J.  A.  Blair.      1S90. 

Drinking  Water  and  Ice  Supplies.  T.  Mitchell  Prudden.  G.  P.  Putnam 
cS:  Sons.     New  York.     1891. 

Potable  Water.      Floyd   Davis.     Silver,  Burdett  &  Co.     New  York.      1891. 

The  Action  of  Water  on  Lead.  John  Henry  Garrett.  H.  K.  Lewis. 
London.     iSgi. 

Treatise  on  Hygiene  and  Public  Health.  Vol.  I.  Thomas  Stevenson  and 
S.  F.  Murphy.     Blakiston,  Son  &  Co.     Phila.     1892. 

Examination  of  Wa'er  for  Sanitary  and  Technical  Purposes.  Henry 
Leffman.     Blakiston,  Son  &  Co.      Phila.      1895. 

Water  Supply  (Considered  Principally  from  a  Sanitary  Standpoint).  W. 
P.  Mason.     John  Wiley  &  Sons.      New  York.      1896. 

Water  Analysis.  J.  A.  Wanklyn  and  E.  T.  Chapman.  Tenth  Ed.  Kegan 
Paul,  Trench,  Trtibner  &  Co.     London.     1896. 

Water  and  Water  Supplies.  John  C.  Thresh.  Rebman  Pub.  Co.  Lon- 
don.     1S96. 

A  Simple  Method  of  Water  Analysis.  John  C.  Thresh.  J.  &  A.  Churchill. 
London.      1S9S. 

Examination  of  Water  (Chemical  and  Bacteriological).  William  P.  Mason. 
John  Wiley  &  Sons.     New  York.     1899. 

The  Microscopy  of  Drinking  Water.  Geo.  C.  Whipple.  John  Wiley  & 
Sons.      New  York.      1899. 

Micro-Organisms  in  Water.  Percy  F.  Frankland  and  Mrs.  Percy  F.  Frank- 
land.     London.      1894. 

Mikroskopische  Wasseranalyse.     Carl  Mez.     J.  Springer,     Berlin.     1898. 

Water  Softening  and  Scientific  Filtration.  Walter  George  Atkins.  E.  & 
F.  N.  Spon.     London.     1880. 

Sewage  Disposal  in  the  United  States.  Geo.  W.  Rafter  and  M.  N.  Baker. 
D.  Van  Nostrand  &  Co.     New  York.     1894. 

Les  Eaux-d'Alimentation,  Epuration,  Filtration,  Sterilization.  Edm. 
Guinochet.     Bailliere  et  Fils.     Paris.     1894. 


BIBLIOGRAPHY.  2  I  5 

The  Filtration  of  Public  Water  Supplies.     Allen   Hazen.     John  Wiley  & 

Sons.     New  York.      1S95. 
Sewage  Disposal  on  the  Farm  and  Protection  of  Drinking  Water.     Theo- 
bald Smith.     U.  S.  Dept.  Agr.,  Farmers'  Bull.  43.      1896. 
Water  and  Its  Purification.     Samuel  Rideal.     London.     1S97. 
Water  Purification  at  Louisville,  Ky.     Geo.  W.  Fuller.     D.  Van  Nostrand 

Co.     New  York.     1S9S. 
Report  on  Water  Purification  at  Cincinnati,  O.     Geo.  W.  Fuller.     Board 

of  Trustees,  Cincinnati.      1899. 
Report  of  Filtration  Commission,  Pittsburgh,  Pa.     1899. 
National  Board  of  Health  Report  for  1882. 
State  Board  of  Health  Reports  for  Massachusetts,  Michigan,  Illinois,  Ohio. 

The    Mass.    Reports,   for   1872-75    and    iSgo-1900,    especially,    contain 

many  valuable  papers,  the  following  being  some  of  the  most  important 

of  them  : 
Chemical  Examination  of  Water  and  Interpretation  of  Analyses.     Thomas 

M.  Drown.      Rep.  Mass.  State  Board  of  Health,  1892,  319. 
Discussion  of  Special  Topics  Relating  to  the  Quality  of  Public  Water  Sup- 
plies.    F.   P.  Stearns  and  T.  M.  Drown.     Rep.  Mass.  State  Board  of 

Health,  1890,  717. 
On  the  Amount  of  Dissolved  Oxygen  contained  in  Waters  of  Ponds  and 

Reservoirs  at   Different   Depths.       Thomas  M.   Drown.      Rep.   Mass. 

State  Board  of  Health,  1S91.  373. 
On  the  Amount   of    Dissolved    Oxygen  contained  in  Waters  of   Ponds  and 

Reservoirs  at  Different  Depths  in  Winter  Under  the  Ice.     Thomas  M. 

Drown.      Rep.  Mass.  State  Board  of  Health,  1S92,  333. 
On  the  Mineral  Contents  of  Some  Natural  Waters  in   Mass.     Thomas  M. 

Drown.     Rep.  Mass.  State  Board  of  Health,  1892,  345. 
The  Effect  of  the  Aeration  of  Natural  Waters.     Thomas  M.  Drown.     Rep. 

Mass.  State  Board  of  Health,  1891,  385. 

In   addition    to  the  above    the  following  papers    contain 
much  information  of  value  on  special  topics  relating  to  water 
supply  and  water  analysis  : 
Chemical    Examination  of  Drinking  Water.     Thomas  M.  Drown>      Proc. 

Soc.  Arts.,  M.  I.  T.,  1887-8,  87. 
The    Analysis  of   Water — Chemical,   Microscopical,    and    Bacteriological. 

Thomas  M.  Drown.     J.  N.  E.  Water  Works  Assoc.  4  (1889),  79. 
On  the  Loss  on  Ignition  in  Water  Analysis.     Thomas  M.  Drown.     Tech, 

Quart.,  2  (1888),  132. 
The   Odor  and   Color   of    Surface   Waters.     Thomas   M.    Drown.      Tech. 

Quart.,  I  (1888),  250. 
Reduction  of   Nitrates   by   Bacteria.     Ellen   H.    Richards  and  George  W. 

Rolfe.     Tech.  Quart.,  9  (1896),  40. 
The    Purification  of   Water    by   Freezing.     Thomas  M.   Drown.     J.  N.  E. 

Water  Works  Assoc,  8  (1893),  46. 


2l6  BIBLIOGRAPHY. 

The  Filtration  of  Natural  Waters.     Thomas  M.  Drown.     J.  of  the  Assoc, 
of  Eng.  Soc,  9  (1890),  356. 

FOOD. 

The  list  given  here  is  limited  to  books  published   since 
1890. 
Traite    G6n6ral    d'Analyse    des    Beurres.       A.     J.    Zune.     H.    Lamartin. 

Paris.      1S92. 
Analyse  des  Matieres  Alimentaires  et  Recherche  de   Leur  Falsifications. 

Ch.  Girard  et  A.  Dupre.     Vve.  Ch.  Dunod  &   P.  Vicq.     Paris.     1894. 
Animal   and    Vegetable    Oils,    Fats,   Butters   and   Waxes.      C.    R.    Alder 

Wright.     Griffin  &  Co.     London.     1894. 
A    Handbook   of    Industrial    Organic    Chemistry.     S.    P.    Sadtler.     J.    B. 

Lippincott  Co.      Phila.      1895. 
Chemistry  of  Wheat,  Flour,  and    Bread.     Wm.  Jago.     Simpkin  Marshall. 

London.      1895. 
Foods  :  Their  Composition  and  Analysis.     Alexander  W.    Blyth.     Griffin 

&  Co.     London.     1896. 
Analysis  of  Milk  and  Milk   Products.      Henry  Lefifman  and  William  Beam. 

Blakiston,  Son  &  Co.      Phila.      1896. 
The  Analysis  of  Food  and  Drugs.     Part  I  :   Milk  and  Milk  Products.     T. 

H.    Pearmain   and  C.  G.   Moor.      Bailliere,   Tindall  &   Cox.      London. 

1897. 
Principles   and    Practice    of    Agricultural    Analysis.     Harvey    W.    Wiley. 

Chem.  Pub.  Co.     Easton,  Pa.      1897. 
Testing  Milk  and  Its  Products.      E.  H.  Farrington  and  F.  W.  Woll.     Men- 

dota  Book  Co.      Madison,  Wis.      iSgS. 
Chemical    Analysis   of  Oils,   Fats,   and  Waxes.     J.    Lewkowitsch.      Mac- 

millan  &  Co.     London.     189S. 
Commercial    Organic    Analysis.     A.    H.    Allen.     Third    Ed.    Rev.    by    H. 

Leffman.      Blakiston,  Son  &  Co.      Phila.      1898. 
Die  Untersuchung    landwirtschaftlich    und    gewerblich    vvichtiger    Stoffe. 

J.  Konig.     Paul  Parey.     Berlin.     1898. 
Our  Secret  Friends  and  Foes.      Percy  Frankland.     London.      1893. 
Die  Menschlichen  Nahrungs-u.  Genussmittel.     J.  Ktinig.    Julius  Springer. 

Berlin.      1893. 
Foods    and    Dietaries.     R.   W.    Burnet,    M.D.     P.    Blakiston,  Son  &  Co. 

Phila.     1893. 
Food  and  Its  Functions.     James  Knight.     Blackie  &  Son.     London.     1895. 
The    Food    Products   of   the   World.     Dr.    Mary    E.    Green.      The    Hotel 

World.     Chicago.     1895. 
The    Story  of  Germ    Life.      H.  W.    Conn.     Appleton  &  Co.     New    York. 

1897. 
The  Relation  of  Food  to  Health.     George  H.  Townshend.     Witt  Publish- 
ing Co.     St.  Louis.     1897. 


BIBLIOGRAPHY.  21J 

Food  Materials    and   Their    Adulterations.  Ellen    H.   Richards.     Home 

Science  Pub.  Co.     Boston.     1898. 

Plain  Words    About    Food.      The   Rumford  Kitchen    Leaflets.     Ellen   H. 

Richards,  Ed.     Home  Science  Pub.  Co.  Boston.     1899. 

The  following  bulletins  of  the  United  States  Department 
•of  Agriculture  will  also  be  found  useful  for  study  or  reference 
on  the  general  question  of  food: 

Office  of  Experiment  Stations,  Bulletins. 
No.    9.   Fermentations  of  Milk.     1892. 

II.   Analyses  of  American  Feeding  Stuffs.      1S92, 
21.   Chemistry  and  Economy  of  Food.      1895. 
25.   Dairy  Bacteriology.      1895. 

28.  (Rev.  Ed.)  Chemical  Composition   of   American    Food    Materials. 

1895. 

29.  Dietary  Studies  at  the  University  of  Tennessee.     1896. 

31.  "  "         "      "  "  "  Missouri.     1896. 

32.  "  "         "      Purdue  University.      1896. 

34.  Carbohydrates  of  Wheat,  Maize,  Flour,  and  Bread.     1896. 

35.  Food  and  Nutrition  Investigations  in  New  Jersey.     1896. 

37.  Dietary  Studies  at  the  Maine  State  College.     1897. 

38.  "  "         — Food  of  the  Negro  in  Alabama.     1897. 
40.         "  "         in  New  Mexico.     1897. 

43.  Composition  and  Digestibility  of  Potatoes  and  Eggs.     1897. 

44.  Metabolism  of  Nitrogen  and  Carbon  in  the  Human  Organism.    1897. 

45.  A  Digest  of  Metabolism  Experiments.     1897. 

46.  Dietary  Studies  in  New  York  City.     1898. 

52.  Nutrition  Investigations  in  Pittsburgh,  Pa.     1898. 

53.  "  "  at  the  University  of  Tennessee.     1898. 

54.  "  "  in  New  Mexico.     1898. 

55.  Dietary  Studies  in  Chicago.     1898. 

63.   Experiments  on  the  Conservation  of  Energy  in  the  Human  Body. 
1899. 

66.  Creatin  and  Creatinin.      1899. 

67.  Bread  and  Bread  Making.      1899. 

69.   Experiments    on   the   Metabolism   of   Matter   and  Energy   in    the 

Human  Body.      1899. 
71.   Dietary  Studies  of  Negroes.     1899. 
75.         "  "         "   University  Boat  Crews.      1900. 

Division  of  Chemistry^  Bulletins. 
No.  13.    Foods  and  Food  Adulteration— (Nine  Parts).      1887-98. 

45.  Analyses  of  Cereals.     1895. 

46.  Official  Methods  of  Analysis.     1895. 
50.  Composition  of  Maize.     1898. 


2  I  8  BIBLIOGRAPHY. 

Farmers'  Bulletins. 
No.  23.   Foods  :  Nutritive  Value  and  Cost.     1894. 
29.   Souring  of  Milk.      1895. 
34.  Meats:  Composition  and  Cooking.     1896. 
74.   Milk  as  Food.     1898. 
85.   Fish  as  Food.     1898. 
93.   Sugar  as  Food.      1899. 
112.   Bread  and  the  Principles  of  Bread  Making.     1900. 


INDEX. 


PAGE 

Acceptable  water,  requirements  for 68 

Acid,  benzoic,  in  milk 169 

,  boric,  in  milk,  detection  of 16S 

,  carbonic,  in  water,  estimation  of 1 1 1 

,  hydrochloric,  reagent  for  iron  determination 2o3 

"  "  "    nitrite  test '. 206 

mercuric  nitrate,  reagent 209 

,  phenol-disulphonic,  reagent 207 

,  salicylic,  in  milk,  detection  of 16S 

"  "wine,         "  " 193 

,  sulphanilic,  reagent  for  nitrite  test 206,  207 

,  sulphuric,  "         "    air  analysis 204 

"  "         "    Kjeldahl  process 207 

Acidity  of  milk,  determination  of 151 

Acids,  in  beer,  "  "  i93 

,  in  wine,  "  " 191 

Adamkiewicz  reaction 186 

Adams'  method  for  fat  in  milk i54 

Adulterants  in  milk 166 

Adulteration,  definition  of I37 

,  extent  of '39 

,  special  cases  of i-4i 

Air,  carbon  monoxide  in - 16 

,  dust  in iS 

,  expired,  composition  of 10 

,  importance  of 3 

,  inspired,  composition  of 10 

,  organic  matter  in 4 ' 

,  water- vapor  in '4 

Albumin,  in  milk,  determination  of 165 

Albuminoid  ammonia,  determination  of  86 

,  relation  to  organic  nitrogen 94 

2ig 


2  20  INDEX. 

PAGE 

Alcohol,  i*i  liquors,  determination  of 190,  193 

,  reagent  for  butter  analysis 210 

,  tables  for  calculating  from  specific  gravity 202 

Alkaline  permanganate,  reagent 205 

Alkalinity  of  milk,  determination  of 152 

water,  "  "    105 

Alum,  in  water,  estimation  of 117 

Amides,  in  wheat,  determination  of 187 

Ammonia-free  water,  reagent 204 

Ammonia,  standard  solution 206 

Aniline  colors, , in  milk,  detection  of i&7 

Annatto,  in  milk,  detection  of 167 

Aqueous  vapor,  table  of  tension  of I95 

Ash,  in  liquors,  determination  of 191,  I93 

of  cereals,  "  " 1  S3 

milk,  composition  of I54 

,  determination  of 153 

Babcock  method  for  fat  in  milk 156 

Barium  hydroxide,  reagent  for  air  analysis 204 

Basic  lead  acetate,  reagent 210 

Beer,  examination  of I93 

"  Behavior  on   ignition  "  of  water  residues .   103 

Bibliography 213 

Biological  examination  of  water x  16 

Biuret  reaction 185 

Brook-water,  characteristics  of 72 

Butter,  ' '  aroma  "  of 1 7 1 

,  complete  analysis  of 181 

,  composition  of ■ iC'9 

Butter-fat,  composition  of 170 

,  examination  of ■  •  •  •   171 

,  rancidity  of I7t 

Calcium  chloride,  standard  solution  of 2o3 

Cane-sugar,  in  milk,  detection  of 166 

Caramel,  in  milk,  detection  of 167 

Carbohydrates,  food  value  of 127 

in  cereals,  estimation  of 18S 

Carbonaceous  matter,  in  water,  estimation  of 98 

Carbon  dioxide  a  disturbing  factor 12 

in  air,  determination  of 27 

in  water,  determination  of in 

,  essential  property  of 21 

,  weight  of  cubic  centimetre  of 196 

monoxide,  in  air,  detection  of 38 


INDEX.  22  1 

PACE 

Carbon-monoxide,  in  air,  determination  of ,, 39 

,  presence  of 16 

Casein,  in  milk,  determination  of 165 

Cazeneuve  reaction 192 

Cereals,  analysis  of 1S2 

,  composition  of > 130 

Chlorine,  in  water,  determination  of 99 

in  well-water  78 

,  source  of  normal 59 

Clark's  method  for  hardness  of  water 103 

Cohen  and  Appleyard  method  for  carbon  dioxide 33 

Collection  of  water  samples ^. 82 

Color  of  waters,  estimation  of iii 

,  source  of 5^ 

standards  for  water  analysis iii 

Coloring-matters,  in  butter,  detection  of 181 

,  in  milk,            "         " 167 

,  in  wine,            "          " 192 

Cream,  in  milk,  estimation  of 150 

"  Crowd-poison  " iS 

Cycle  of  nitrogen 53 

Defren's  method  for  milk-sugar. 163 

Dietaries. .    '32 

Dissolved  oxygen,  in  water,  determination  of 107 

Dust,  in  air,  estimation  of ■  •  •  •  42 

,  presence  of 18 

Edestin,  in  wheat,  determination  of 187 

Erythrosine,  reagent  for  water  analysis 208 

Ether,  anhydrous,  reagent 210 

Expired  air,  composition  of 10 

Extract,  in  liquors,  determination  of I9'>  '93 

Extraction  apparatus  for  fat  in  milk 156 

Fat,  in  milk,  methods  for  estimation  of I54 

Fats  and  oils,  in  cereals,  estimation  of i ^3 

,  food  value  of '  ••  •  '20 

Fehhng's  solution,  reagent  for  sugars 209 

Fibre,  crude,  determination  of '89 

Filtration 74 

Fitz's  method  for  carbon  dioxide 35 

Fixed  acids  in  butter,  estimation  of '74 

Food,  chief  dangers  in  use  of   142 

,  definition  of '23 

,  necessity  for  examination  of ^ 


222  INDEX. 


PAGE 


Food,  importance  of 5 

,  methods  of  analysis  of 146 

principles 1 24 

,  sanitary  aspect  of 7 

values,  necessity  for  knowledge  of 133 

,  variation  in  nitrogen  content 7 

Food-materials,  one  hundred  common ,- 130 

Formaldehyde,  in  milk,  detection  of 16S 

Formulae  for  milk  analysis 15^ 

Free  ammonia,  in  water,  determination  of 86 

Fuchsine,  in  wine,  detection  of ic)2 

Fuchsin-sulphurous  acid,  reagent 2og 

Gasolene,  reagent 209 

Gliadin,  in  wheat,  determination  of 187 

Glutenin,  in  wheat,  determination  of 1S7 

Glycerine-soda,  reagent  for  butter  analysis 210 

Ground-water,  history  of 50 

Hardness  of  water,  determination  of 103 

,  table  for 200 

Heat  of  combustion 128 

Hehner's  method  for  butter  analysis 174 

hardness  of  water 105 

Hiibl  method  for  butter  analysis 1^5 

Ice,  rules  for  use  of 60 

Ilosvay's  method  for  nitrites  in  water 05 

Inspired  air,  composition  of jo 

Iodine  value,  in  butter,  determination  of 175 

lodo-mercuric  solution,  reagent 210 

Iron,  in  water,  determination  of 106 

,  standard  solution  for  water  analysis 208 

Kjeldahl  method  for  nitrogen .g2,  1S3 

,  how  modified  for  nitrates i S5 

,  theory  of 1S4 

Kubel's  method  for  "  oxygen  consumed  " g8 

Lake-water,  characteristics  of 72 

Lead,  in  water,  determination  of nS 

,  standard  solution  for  water  analysis 209 

Leflman-Beam  method  for  butter  analysis 174 

Leucosin,  in  wheat,  determination  of 187 

Liebermann's  test 1S6 

Lime-water,  standard  for  air  analysis 204 


INDEX.  223 

PAGE 

Liquors,  fermented,  examination  of igo 

"  Loss  on  ignition"  in  water  analysis loi 

"  Luftprufer,"  Wolpert's 37 

Malt  extract,  preparation  of 1S9 

Manganous  sulphate,  reagent  for  oxygen 20S 

.  Mechanical  ventilation,  principles  of 23 

Melting-point  of  butter,  determination  of 178 

Micro-organisms,  in  air,  estimation  of 40 

Microscopic  examination  of  butter 177 

Milk,  fermentations  of 14S 

"  Milk  of  alumina,"  reagent  for  water  analysis 207 

,  percentage  composition  of 147 

,  reaction  of 151 

Milk-scale,  Richmond's 160 

Milk-sugar,  determination  of 161 

,  optical  determination  of 164 

Millon's  reaction 1S6 

reagent,  preparation  of 211 

Mineral  salts,  in  food,  importance  of 128 

,  in  water 59 

,  presence  of,  in  potable  water 79 

Moisture,  in  cereals,  determination  of 182 

Muscular  activity  and  respiratory  exchange 15 

Naphtylamine  acetate,  reagent 207 

hydrochlorate,  reagent 206 

Natural  ventilation,  principles  of 22 

Nessler's  reagent,  preparation  of 205 

Nitrate,  standard  solution  for  water  analysis 207 

Nitrates,  in  water,  determination  of 9^ 

Nitrite,  standard  solution  for  water  analysis 206 

Nitrites,  in  air,  determination  of 39 

,  in  water,  determination  of 94 

Nitrogen  essential  to  living  matter 63 

,cycleof 53 

,  in  beer,  determination  of ^91 

,  in  well-water  77 

Nitrogenous  compounds,  why  dangerous 64 

matter,  results  of  decay  of 64 

substances,  importance  of 125 

Normal  waters,  table  of 'O^ 

Nutritive  ratio '29 

Odor  of  water,  analytical  value  of 74 

,  detection  of "4 


224  INDEX. 

lAGE 

Opacity  of  milk,  measurement  of 15a 

Organic  carbon  in  water 65 

matter,  in  air,  determination  of 41 

nitrogen,  in  water,  determination  of 92 

Organisms  in  water,  work  of 55 

Orseille,  in  wine,  detection  of iq2 

"  Oxygen  consumed,"  determination  of 98 

Oxygen  dissolved  in  water,  determination  of 107 

,  table  of  saturation 200 

Pettenkofer  method  for  carbon  dioxide 28 

Phospho-tungstic  acid,  reagent 210 

Physical  methods  of  butter  analysis 177 

Polluted  waters,  examples  of 199 

Popular  tests  for  carbon  dioxide 33 

Potassium  chromate,  reagent  for  water  analysis 207 

ferrocyanide,  reagent  for  water  analysis 209 

hydroxide,  reagent  for  butter  analysis 210 

,  for  Kjeldahl  method . .  .207,  210 

iodide,  reagent  for  butter  analysis 210 

dissolved  oxygen 208 

permanganate,  reagent  for  iron 208 

sulphide,  reagent 2io 

sulphocyanide,  reagent  for  iron 208 

Predigested  foods 13& 

Preservatives  in  milk 168 

Pressure,  influence  on  respiratory  exchange 12 

Problem  of  safe  water 62 

Proteids,  in  cereals,  determination  of  total 183 

milk,  determination  of  total 165 

,  qualitative  tests  for 185 

,  separation  of 186 

Pumice  for  butter  analysis 209 

"  Purified  "  water,  definition  of 57 

"  Radiator"  for  igniting  water  residues loi 

Reaction  of  milk. .  .  .    151 

Refractive  index  of  butter,  determination  of 17S 

Reichert-Meissl  number,  determination  of 172 

Relation  of  water  to  health 52 

Residue,  in  water,  determination  of loi 

Respiratory  exchange,  explanation  of 10 

quotient 14 

River-water,  characteristics  of 73 

Salt,  in  butter,  determination  of iSi 

,  in  milk,  determination  of 166 

Sanitary  chemistry,  scope  of i 


INDEX. 


225 


PAGE 

Sanitary  science,  importance  of 2 

water  analysis,  principles  involved  in 66 

Saponification  of  butter-fat 173 

Sediment,  in  water,  estimation  of 116 

Sewage,  typical  analyses  of igq 

Shallow  wells,  characteristics  of  water  from 77 

Soap,  standard  solution  for  water  analysis 208 

Sodium  carbonate,  in  milk,  detection  of i6g 

chloride,  standard  solution  for  water  analysis 207 

Sodium  hydroxide,  reagent  for  dissolved  oxygen ' 208 

thiosulphate,  reagent  for  dissolved  oxygen 20S 

Soot,  in  air,  estimation  of 42 

Sophistication,  meaning  of -. 137 

Specific  gravity  of  butler,  estimation  of   178 

of  milk,  estimation  of i^g 

,  table  for  correcting 201 

Starch,  in  cereals,  determination  of -. 1S8 

milk,  detection  of 166 

Statement  of  results  in  water  analysis 119^ 

Storage  of  water,  results  of 57 

Sucrose,  in  milk,  detection  of 166 

Sugars,  in  cereals,  determination  of 188 

Surface  water,  characteristics  of 71 

,  summary  of 75 

Tension  of  aqueous  vapor,  table  of ig5 

Total  solids,  in  milk,  determination  of 152 

Trade  names 140 

Turbidity  and  sediment,  cause  of 74 

Turbidity  of  water,  estimation  of 116 

Ventilation,  requirements  of 26 

,  to  test  efficiency  of 24 

Vital  capacity,  definition  of 10 

Volatile  acids,  in  butter,  determination  of 172 

Water,  added,  determination  of,  in  milk 166 

Water  analysis,  blank  form  for 120 

,  limits  of , 69 

,  value  of 80 

,  circulation  of,  on  the  earth •.  47 

,  illustration  of  contamination  of 48 

,  daily  quantity  needed 4 

free  from  ammonia,  reagent 204 

,  general  use  of 5 

in  butter,  determination  of 178 

,  legal  restrictions  upon  use  of       43 


226  INDEX. 

PAGE 

Water,  methods  of  analysis  of 82 

,  mineral  contents  of 199 

need  of 4 

,  preliminary  inspection  of  source  of 66 

,  solvent  power  of 51 

,  table  of  average  composition  of 197 

,  the  ideal  drinking 45 

classification  of 71 

Water-pipes,  danger  from 80 

Water-vapor  in  air   14 

Well  and  spring  waters,  characteristics  of 76 

Werner-Schmid  method  for  fat  in  milk 157 

Wine,  analysis  of. .    190 

,  specific  gravity  of 190 

Winkler's  method  for  dissolved  oxygen  in  water 107 

Wolpert's  method  for  carbon  dioxide 37 

Xanthoproteic  reaction 186 


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-AIJ-HERN  REG10N4L  L'B"*",\."j;li!I;^ 


MARGARET  CARNF.r.lF   i  iroadv 


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